Hydrogen peroxide production in microchannel reactors

ABSTRACT

The present invention includes methods and apparatuses that utilize microchannel technology and, more specifically in exemplary form, producing hydrogen peroxide using microchannel technology. An exemplary process for producing hydrogen peroxide comprises flowing feed streams into intimate fluid communication with one another within a process microchannel to form a reactant mixture stream comprising a hydrogen source and an oxygen source such as, without limitation, hydrogen gas and oxygen gas. Thereafter, a catalyst is contacted by the reactant mixture and is operative to convert a majority of the reactant mixture to hydrogen peroxide that is withdrawn via an egressing product stream. During the hydrogen peroxide chemical reaction, exothermic energy is generated. This exothermic energy is absorbed by the fluid within the microchannel as well as the microchannel itself. In a preferred embodiment, a heat exchange fluid is in thermal communication with the microchannel housing the exothermic reaction and is operative to absorb a portion of this exothermic energy and transfer such energy from the microchannel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/116,148, filed Apr. 27, 2005, now U.S. Pat. No. ______, which claimedpriority to U.S. Provisional Patent Application Ser. No. 60/565,629,filed Apr. 27, 2004, and entitled “HYDROGEN PEROXIDE PRODUCTION INMICROCHANNEL REACTORS,” the disclosure of which is incorporated hereinby reference.

RELATED ART

1. Field of the Invention

The present invention is directed to methods and apparatuses thatutilize microchannel technology and, more specifically in exemplaryform, producing hydrogen peroxide using microchannel technology.

2. Introduction of the Invention

Hydrogen peroxide is a fast growing, high volume industrial chemicalwith an expected growth rate of 6% to 10% annually. It is one of themost common bleaching agents, used mainly in the textile, pulp and paperindustries. The decomposition products of hydrogen peroxide are waterand oxygen, thereby minimizing the environmental impact of effluents.

Hydrogen peroxide is typically manufactured by a process known asautooxidation (AO), which is organic solvent based. Hydrogen peroxidecan be produced up to 70% by weight concentration through an energyintensive distillation stage. FIG. 1 illustrates an exemplary AO processfor the formation of hydrogen peroxide. Below is a brief description ofthe major component stages of an AO process.

Hydrogenation—The working solution is composed of anthraquinones incertain organic solvent(s). The working solution enters the hydrogenatorwhere anthraquinones react with hydrogen in the presence of a catalystto form the corresponding hydroquinones.

Oxidation—The hydroquinones are oxidized to quinones with oxygen(usually air) resulting in simultaneous formation of hydrogen peroxide.Before the hydrogenated working solution that contains hydroquinones canbe fed to the oxidation step, the catalyst used in the hydrogenationstep has to be filtered out. This is particularly important because thehydrogenation catalysts used in the AO process (palladium and Raneynickel) also catalyze the decomposition of hydrogen peroxide. A smallamount of these catalysts in the oxidation and extraction steps may leadto considerable loss of hydrogen peroxide and serious disturbances.

Extraction and Recovery of the Working Solution—The oxidized workingsolution from the oxidation stage is then treated with water to extracthydrogen peroxide. The working solution leaving the extraction unit mustbe adjusted to a specific water content before being returned to thehydrogenation step. The working solution is purified and regenerated inregeneration units (not shown in FIG. 1).

SUMMARY OF THE INVENTION

The present invention is directed to methods and apparatuses thatutilize microchannel technology and, more specifically in exemplaryform, producing hydrogen peroxide using microchannel technology. Anexemplary process for producing hydrogen peroxide comprises flowing feedstreams into intimate fluid communication with one another within aprocess microchannel to form a reactant mixture stream comprising ahydrogen source and an oxygen source such as, without limitation,hydrogen gas and oxygen gas. Thereafter, a catalyst is contacted by thereactant mixture and is operative to convert a majority of the reactantmixture to hydrogen peroxide that is withdrawn via an egressing productstream. During the hydrogen peroxide chemical reaction, exothermicenergy is generated. This exothermic energy is absorbed by the fluidwithin the microchannel as well as the microchannel itself. In apreferred embodiment, a heat exchange fluid is in thermal communicationwith the microchannel housing the exothermic reaction and is operativeto absorb a portion of this exothermic energy and transfer such energyfrom the microchannel.

The invention also includes an apparatus for carrying out a hydrogenperoxide reaction within a microchannel reactor as well as methodsassociated therewith. Such methods include features such as, withoutlimitation, operating parameters for start-up and shutdown of amicrochannel reactor and scale-up procedures to accommodate variousreactant volumetric throughputs.

The invention includes manifolds and manifold designs for distributingfluids to and from the microchannel embodiments discussed herein. Theinvention further includes microchannels and microchannel fabricationtechniques for promoting mass transfer between catalyst and reactants.Still further, the invention includes aspects of process control for ahydrogen peroxide process carried out using microchannel technology.These and other aspects of the present invention are discussed morefully below. Therefore, for a complete summary of the present invention,reference is had to the entire disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary autooxidation process forthe production of hydrogen peroxide;

FIG. 2 is a schematic illustration of a microchannel that may be usedwith the inventive process;

FIG. 3 is a schematic flow sheet illustrating the inventive process in aparticular form wherein H₂ and O₂ flow in a microchannel reactor incontact with a catalyst and react to form hydrogen peroxide;

FIG. 4 is a schematic illustration of a repeating unit of processmicrochannels and heat exchange microchannels that may be used in themicrochannel reactor core of the microchannel reactor illustrated inFIG. 3;

FIG. 5 is a schematic illustration of another repeating unit of aprocess microchannel and a heat exchange microchannel that may be usedin the microchannel reactor core of the microchannel reactor illustratedin FIG. 3;

FIG. 6 is a schematic illustration of another repeating unit of processmicrochannels and heat exchange microchannels that may be used in themicrochannel reactor core of the microchannel reactor illustrated inFIG. 3;

FIG. 7 is a schematic illustration of another repeating unit of processmicrochannels and heat exchange microchannels that may be used in themicrochannel reactor core of the microchannel reactor illustrated inFIG. 3;

FIG. 8 is a schematic illustration of another repeating unit of processmicrochannels and heat exchange microchannels that may be used in themicrochannel reactor core of the microchannel reactor illustrated inFIG. 3;

FIG. 9 is a schematic illustration of another repeating unit of processmicrochannels and heat exchange microchannels that may be used in themicrochannel reactor core of the microchannel reactor illustrated inFIG. 3;

FIG. 10 is a schematic illustration of another repeating unit of processmicrochannels and heat exchange microchannels that may be used in themicrochannel reactor core of the microchannel reactor illustrated inFIG. 3;

FIG. 11 is a schematic illustration of another repeating unit of processmicrochannels and heat exchange microchannels that may be used in themicrochannel reactor core of the microchannel reactor illustrated inFIG. 3;

FIG. 12 is a further exemplary stream layout for hydrogen peroxideproduction in accordance with the present invention;

FIG. 13 a is another alternate stream layout for hydrogen peroxideproduction in accordance with the present invention;

FIG. 13 b is a further alternate stream layout for hydrogen peroxideproduction in accordance with the present invention;

FIG. 13 c is another alternate stream layout for hydrogen peroxideproduction in accordance with a third alternate exemplary embodiment ofthe present invention;

FIG. 13 d is a further alternate stream layout for hydrogen peroxideproduction in accordance with the present invention;

FIG. 13 e is another alternate stream layout for hydrogen peroxideproduction in accordance with the present invention;

FIG. 14 is an exemplary stream layout for hydrogen peroxide productionin accordance with the present invention;

FIG. 15 is a schematic diagram of a microchannel absorber in accordancewith the present invention;

FIG. 16 is a partial schematic diagram of a microchannel absorber inaccordance with the present invention;

FIG. 17 is a side view of a horizontal pressure vessel housing ahydrogen peroxide microchannel reactor in accordance with the presentinvention;

FIG. 18 includes two exemplary vertical cross-sections taken along line8-8 of the horizontal pressure vessel of FIG. 17;

FIG. 19 is a side view of a vertical pressure vessel housing a hydrogenperoxide microchannel reactor in accordance with the present invention;

FIG. 20 is a horizontal cross-section taken along line 10-10 of thevertical pressure vessel of FIG. 19;

FIG. 21 illustrates exemplary features that enhance heat transfercharacteristics while regulating the flow in connecting channels;

FIG. 22 illustrates the geometry assumed for flow distribution casestudy of Example X, with manifold and channel heights of 1.02 mm;

FIG. 23 illustrates mass flowrate versus channels in the case study ofExample X;

FIG. 24 is a table listing lengths of flow distribution features used inthe case study of Example X;

FIG. 25 illustrates a flow distribution by channel for case of Example Xincluding flow distribution features of the present invention;

FIG. 26 illustrates a stack of lamina designed to create varying channelheights along the length of a microchannel to make the pressure drop ofthe flow network more uniform and thus improve flow distribution;

FIG. 27 illustrates a model of microchannel after bonding, where themicrochannel to the farthest left has a higher flow resistance than themicrochannel to the farthest right;

FIG. 28 illustrates a nibbling approach to varying lengths of slots;

FIG. 29 illustrates an exemplary cross-section of a microchannel;

FIG. 30 is a schematic diagram of an exemplary single feedback controlloop; and

FIG. 31 is an illustration of the proportional control component inrelation to gain K.

FIG. 32 is an exemplary diagram of a microchannel having components toenhance flame acceleration and turbulence therein in accordance with thepresent invention;

FIG. 33 is an exemplary diagram of a microchannel having components tosuppress flame turbulence and induce flame stretching therein inaccordance with the present invention;

FIG. 34 is a schematic illustration of a process microchannel that maybe used with the inventive process, the process microchannel containinga catalyst having a flow-by configuration;

FIG. 35 is a schematic illustration of a process microchannel that maybe used with the inventive process, the process microchannel containinga catalyst having a flow-through configuration;

FIG. 36 is a computational fluid dynamics (CFD) simulation indicative ofa thickness of liquid layer directly after draining in a verticalchannel having a gap of 0.04 inches;

FIG. 37 is a representation of the effect of contact angle on liquidhold-up associated with a microfin/groove;

FIG. 38 is a schematic illustration of a process microchannel that maybe used in the inventive process, the process microchannel containing afin assembly comprising a plurality of fins, a catalyst being supportedby the fins;

FIG. 39 illustrates an alternate embodiment of the process microchanneland fin assembly illustrated in FIG. 38; and

FIG. 40 illustrates another alternate embodiment of the processmicrochannel and fin assembly illustrated in FIG. 38.

FIG. 1A1 shows a three opening manifold with mass flux rates (G), staticpressures (P) and constant connection channel widths (W_(cc)).

FIG. 1B1 shows dimensions for a three opening header manifold.

FIG. 2A1 illustrates the static pressure profile in an M2M based onturbulent pipe turning loss and momentum compensation coefficients forthe Z-manifold. Channel #1 is the first channel seen in the header, #19the last channel seen by the footer. The diamonds show pressure in theheader and the squares show pressure drop in the footer.

FIG. 2B1 illustrates M2M header manifold momentum compensationcoefficients for an connection to manifold cross-sectional area ratio of0.09 for several M2M header manifold mass flow rate ratios (MFR), theratio of the mass flow rates downstream to upstream of a connectingchannel.

FIG. 2C1 illustrates experimentally obtained M2M header manifold turningloss coefficients versus the channel mass flow rate ratio (connectingchannel to manifold upstream of connecting channel) for a connection tomanifold cross-sectional area ratio of 0.09. Also plotted are the headermanifold turning loss coefficients for conventional turbulent circularpipes (solid line for the same connection to manifold cross-sectionalarea ratio).

FIG. 2D1 illustrates negative footer turning loss coefficients for aconnection to manifold cross-sectional area ratio of 0.09 inconventional pipes and an M2M manifold.

FIG. 3A1 illustrates a set of sub-manifolds for a Z-manifold system.

FIG. 3B1 illustrates a L-manifold system containing two submanifolds.

FIG. 3C1 illustrates an example of a grate for a stacked shim systemwith the grate extending across the M2M manifold channel's width.

FIG. 3D1 illustrates a grate design with a grate pulled into themanifold.

FIG. 3E1 illustrates a “Gate” design formed by an upper gate shim and alower channel shim. The gray (upper) shim makes the opening with the M2Mmanifold and the lower “picture frame” shim makes a plane fordistribution to the connecting channels, of which an example of four areshown here for each gate.

FIG. 3F1 illustrates the “Gate” design of FIG. 3E1 where the shims havebeen inverted across the major central plane.

FIG. 3G1 illustrates decreasing cross-sectional area of the gates in thedirection of flow.

FIGS. 41-221 illustrate shim designs that were assembled to constructand integrated combustion reactor.

FIG. 231 illustrates a manifold used to separate phases.

FIG. 241 illustrates a manifold with gates of decreasing channel widthin the direction of manifold flow to obtain a more equal flowdistribution.

FIG. 25 a 1 illustrates a design with gates and submanifold zones.

FIG. 25 b 1 illustrates a manifold with a straightening zone.

FIG. 25 c 1 is an exploded view of the laminate of FIG. 25 b 1.

FIGS. 26 a 1, 26 b 1 and 271 illustrate flow bumps in channels made by ashim construction.

FIG. 281 illustrates a cross flow manifold with openings for mixing.

FIG. 291 illustrates an inclined manifold.

FIG. 301 schematically illustrates angled openings between a manifoldand a set of connecting channels.

FIG. 31 illustrates a channel design with offset regions forinterchannel mixing.

FIG. 32 illustrates a gate design in which porous bodies provide equalflow.

FIG. 33 illustrates a flexible wall projection that alters flow througha channel.

FIG. 34A1 schematically illustrates a macromanifold connected to twomicrodevices.

FIG. 34B1 illustrates a non-divergent header with convergent footer andmultiple inlets and outlets parallel the direction of flow. Louvers canbe used to direct flow.

FIG. 351 illustrates a central flow redistributed by a flow distributionplate.

FIG. 361 illustrates an exploded view schematic of a high-pressurevaporizer showing the center-fed inlet, the first and second plates anda two-dimensional channel array in orthogonal shims. Flow is collectedon the opposite side of the channel array with a centrally locatedoutlet pipe, directly opposite the inlet pipe entrance.

FIG. 37 illustrates a manifold design with nonaligned orifice plates.

FIG. 38 is a cross-sectional, top down view of a device in which theheader contains orifice plates.

FIGS. 39A1 and 39B1 illustrate a cross-flow reactor utilizing a moveabledistribution plate.

FIG. 401 shows channel mass flux rates in connecting channels accordingto the analysis in comparative Example 1 using 10⁻⁰⁶ kg/s of air.

FIG. 411 shows channel mass flux rates in connecting channels accordingto the analysis in comparative Example 1 using 10⁻⁰⁶ kg/s of air at roomtemperature and pressure with developing flow and all momentum termsincluded.

FIG. 421 shows channel mass flux rates in connecting channels accordingto the analysis in comparative Example 1 using 10⁻⁰⁶ kg/s of water atroom temperature with developing flow and all the momentum termsincluded.

FIG. 431 shows channel mass flux rates in connecting channels accordingto the analysis in comparative Example 1 using 10⁻⁰⁶ kg/s of water withwider header and footer widths with developing flow and all momentumterms included.

FIG. 441 shows channel mass flux rates in connecting channels accordingto the analysis in comparative Example 1 using 10⁻⁰⁵ kg/sec (10× that ofFIG. 431) with wider header and footer widths with developing flow andall momentum terms included.

FIG. 451 shows predicted static gage pressures in an air M2M manifoldfor the header and in the gate plotted versus fuel gate number fromExample 2. Air gate number 1 corresponds to air sub-manifold 1, gate 1,while fuel gate number 18 corresponds to sub-manifold 6, gate 3.

FIG. 461 shows predicted static gage pressures in an fuel M2M manifoldfor the header and in the gate plotted versus fuel gate number fromExample 2. Fuel gate number 1 corresponds to fuel sub-manifold 1, gate1, while fuel gate number 18 corresponds to sub-manifold 6, gate 3.

FIG. 471 shows predicted channel mass flow rates for the air and fuelchannels plotted versus fuel channel number for Example 2. Fuel channel1 is channel 1 of sub-manifold 1 and fuel channel 72 is channel 12 ofsub-manifold 6.

FIG. 481 shows mass flow rate distribution for the air manifold testpiece of Example 3 plotted versus channel number. Channel 1 is closestto the manifold entrance while channel 12 is the farthest away.

FIG. 491 is a plot of static pressure as a function of distance of thechannel position from the submanifold entrance.

FIG. 501 illustrates channel flow distribution from Example 4 for a2.00″ wide M2M channel with M=0.160″, L=0.120″ and B=0.5.

FIG. 511 illustrates minimum quality index factors plotted versusconnecting channel to manifold pressure drop ratio (PDR₂) as explainedin Example 5.

FIG. 51 illustrates minimum quality index factors plotted versusconnecting channel to manifold pressure drop ratio (PDR₁) as explainedin Example 5.

DETAILED DESCRIPTION

The exemplary embodiments of the present invention are described andillustrated below to encompass devices and methods of utilizingmicrochannel process technology and, in exemplary form, for producinghydrogen peroxide using a microchannel unit operation. Of course, itwill be apparent to those of ordinary skill in the art that thepreferred embodiments discussed below are exemplary in nature and may bereconfigured without departing from the scope and spirit of the presentinvention. However, for clarity and precision, the exemplary embodimentsas discussed below may include optional steps, methods, and featuresthat one of ordinary skill should recognize as not being a requisite tofall within the scope of the present invention.

An exemplary hydrogen peroxide production process involves anaqueous-based direct reaction between a source of hydrogen and an oxygensource. In exemplary form, a source of hydrogen includes any chemicalcompound or element capable of donating one or more hydrogen atoms orions, whereas an oxygen source includes any chemical compound or elementcapable of donating one or more oxygen atoms or ions. This exemplaryprocess generates no appreciable wastes, uses less energy per unitvolume of hydrogen peroxide product produced as compared to anautooxidation (AO) process, and has lower capital and operating costs incomparison to commercial AO processes. These savings are attributable toa simplified plant design that eliminates costly solvent recovery unitsrequire to separate hydrogen peroxide from the organic working solutionof an AO process. In addition, this exemplary process provides ahydrogen peroxide aqueous solution product in a market ready form,without requiring dilution.

Most hydrogen peroxide commercial applications use low concentrations ofhydrogen peroxide (about 15% by weight), in direct contrast to the 70%by weight hydrogen peroxide solution produced in the AO processes. Endusers are interested in on-site and on-demand hydrogen peroxidegeneration that reduces transportation costs, storage costs, andexpenses associated with diluting the hydrogen peroxide concentrate.However, combining H₂ and O₂ in conventional reactor systems isdifficult at H₂ concentrations above about 5% by weight, as the mixturebecomes flammable and even explosive. At low H₂ concentrations, the rateof H₂ diffusion in the liquid phase is extremely slow, thus makingadvantageous the use of very high pressures, and rendering the processenergy more inefficient. The solubility of H₂ in the liquid phase can beimproved by adding H₂SO₄ and halide ions, but both may pose corrosionand contamination problems.

The present invention is described below by way of several examples. Theexamples include discussion of gas and liquid phase systems, where onephase may be designated as the continuous phase and the other may bedesignated as the dispersed phase. The examples may also make use ofmultiple streams of liquids, gases, and/or liquid/gas mixtures.

The term “microchannel” refers to a channel having at least one internaldimension of height or width of up to about 10 millimeters (mm), and inone exemplary embodiment up to about 5 mm, and in a further exemplaryembodiment up to about 2 mm, and in still a further exemplary embodimentup to about 1 mm. An example of a microchannel that may be used with theinventive process as a process microchannel and/or a heat exchangemicrochannel is illustrated in FIG. 2. The microchannel 10′ illustratedin FIG. 2 has a height (h), width (w) and length (l). Fluid flowsthrough the microchannel 10′ in a direction that is perpendicular toboth the height and width as indicated by directional arrows 12′ and14′. The height (h) or width (w) of the microchannel may be in the rangeof about 0.05 to about 3 m. In one embodiment the height or width mayrange from about 0.15 to about 3 m. The length (l) of the microchannelmay be of any dimension, for example, up to about 10 meters. Althoughthe microchannel 10′ illustrated in FIG. 2 has a cross section that isrectangular, it is to be understood that the microchannel may have across section having any shape, for example, a square, circle,semi-circle, trapezoid, etc. The shape and/or size of the cross sectionof the microchannel may vary over its length. For example, the height orwidth may taper from a relatively large dimension to a relatively smalldimension, or vice versa, over the length of the microchannel.

The term “microchannel reactor” refers to a reactor wherein a chemicalreaction is conducted in a microchannel.

The term “adjacent” when referring to the position of one channelrelative to the position of another channel means adjacent such that awall separates the two channels. This wall may vary in thickness.

The term “fluid” refers to a gas, a liquid, or a gas or a liquidcontaining dispersed solids, or a mixture thereof. The fluid may be inthe form of a gas containing dispersed liquid droplets. The fluid may bein the form of a liquid containing dispersed liquid or gas droplets.

The term “contact time” refers to the volume of the reaction zone withinthe microchannel reactor divided by the volumetric feed flow rate of afluid flowing through the reaction zone at a temperature of 0° C. and apressure of one atmosphere.

The term “reaction zone” refers to a space within a microchannel whereina catalyst is positioned.

The term “residence time” refers to the internal volume of a space(e.g., the reaction zone within a microchannel reactor) occupied by afluid flowing through the space divided by the volumetric flowrate forthe fluid flowing through the space at the temperature and pressurewithin the space.

The term “conversion of O₂” refers to the O₂ mole change between thefluid entering the process microchannels and the fluid exiting theprocess microchannels divided by the moles of O₂ in the fluid enteringthe process microchannels.

The term “conversion of H₂” refers to the H₂ mole change between thefluid entering the process microchannels and the fluid exiting theprocess microchannels divided by the moles of H₂ in the fluid enteringthe process microchannels.

The term “Acycle@” is used herein to refer to a single pass of thereactants through the process microchannel.

As is standard patent terminology, “comprising” means “including” andneither of these terms exclude the presence of additional or pluralcomponents. For example, where a device comprises a lamina, a sheet,etc., it should be understood that the inventive device may includemultiple laminae, sheets, etc.

The “channel axis” is the line through the center of a channel'scross-section as it extends through the channel.

“Bonding” means attaching or adhering, and includes diffusion bonding,gluing, brazing and welding.

A “bump” is an obstruction or area of increased channel wall roughnessthat reduces mass flow rate through a channel under typical operatingconditions.

Capacity of a manifold, Cman, is defined as the mass processed per unitvolume of manifold:

$\begin{matrix}{C_{man} = \frac{m_{man}}{V_{man}}} & (1)\end{matrix}$

wherem_(man) [kg/sec]=Mass flow rate for a manifoldV_(man) [m3]=The total volume of the manifold: the manifold channels;internal distribution features, such as sub-manifolds and gates, gratesand other manifold connection channels, including their containmentwalls; the external containment walls of the manifold, including spacebetween manifold channels not used for other manifolds or processingchannels. The total volume of the manifold does not include the channelwalls in the layers directly above or below the manifold channel. Theexternal containment wall volume in an M2M manifold includes that volumethat separates the manifold from the necessary device perimeter of amicrochannel device, which occurs around the entire device. It includesthe wall volume separating the channels of fractal distributionmanifolds that aren't used by other connecting channels.

For microchannel devices with M2M manifolds within the stacked shimarchitecture, the M2M manifolds add to the overall volume of the deviceand so it is desirable to maximize the capacity of the manifold. Inpreferred embodiments of the invention, an M2M distributes 1 kg/m3/s,preferably 10 kg/m3/s, and in some preferred embodiments distributes 30to 150 kg/m3/s.

The connections between the manifold and the connecting channels (i.e.,the M2M distribution structures) described herein preferably havethicknesses (i.e., heights) of 20 μm to 5 mm, more preferably 2 mm orless, and preferably have widths in the range of 100 μm to 5 cm and insome preferred embodiments have widths more than 250 micrometers andless than one millimeter. The lengths of the connecting channels have alower limit of zero and an upper limit of 1 meter, and in some preferredembodiments a range of 2 millimeters to 10 cm.

The cross-sectional area of a channel is that cross-sectional planenormal to the channel axis. It excludes the cross-sectional area of thewall and any applied coatings (catalyst, bonding, metal protection) tothe wall. A layer typically includes plural channels that are separatedby channel walls. The cross-sectional area of a channel includes areataken up by catalyst, if present.

Channels are defined by channel walls that may be continuous or maycontain gaps. Interconnecting pathways through a monolith foam or feltare not connecting channels (although a foam, etc. may be disposedwithin a channel).

“Connecting channels” are channels connected to a manifold. Typically,unit operations occur in connecting channels. Connecting channels havean entrance cross-sectional plane and an exit cross-sectional plane.Although some unit operations or portions of unit operations may occurin a manifold, in preferred embodiments, greater than 70% (in someembodiments at least 95%) of a unit operation occurs in connectingchannels. A “connecting channel matrix” is a group of adjacent,substantially parallel connecting channels. In preferred embodiments,the connecting channel walls are straight.

The “connection to manifold cross-sectional area ratio” is the ratio ofthe cross-sectional area of open area of the manifold connection (suchas a gate or grate) to the cross-sectional area (perpendicular to thecentral axis) of the manifold at the position immediately upstream ofthe connection (for a header) or immediately downstream of a connection(for a footer).

The connecting channel pressure drop (DPCCdP) is the static pressuredifference between the center of the entrance cross-sectional plane andthe center of the exit cross-sectional plane of the connecting channels.In some preferred embodiments, connecting channels are straight withsubstantially no variation in direction or width. The connecting channelpressure drop for a system of multiple connecting channels is thearithmetic mean of each individual connecting channel pressure drop.That is, the sum of the pressure drops through each channel divided bythe number of channels. For the examples, pressure drops are unadjusted;however, in the claims, pressure are defined based on the channels thatcomprise 95% of the net flow through the connecting channels, the lowestflow channels are not counted if the flow through those channels is notneeded to account for 95% of the net flow.

The FA dimensionless number is a means of distinguishing high momentumflow from creeping flow in manifolds:

$\begin{matrix}{{FA} = {\frac{\left\lbrack {0.058 + {0.0023\left( {\ln \mspace{11mu} {Re}} \right)^{2}}} \right\rbrack^{2}D}{L_{M\; 2M}} < 0.01}} & (2)\end{matrix}$

where Re is the manifold Reynolds number, D is the manifold hydraulicdiameter and LM2M is the manifold zone length. The header manifoldReynolds number and hydraulic diameter for FA are defined at theposition on the channel axis where the wall plane closest to the headerentrance belonging to the connecting channel closest to the entrance inthe manifold connects with the channel axis. The footer manifoldReynolds number and hydraulic diameter for FA are defined at theposition where the wall plane closest to the footer exit belonging tothe connecting channel closest to footer exit connects with the channelaxis. FA should be below 0.01 and for some preferred embodiments lessthan 0.001.

A “flow resistor” is a bump, grate, or porous body. A flow resistor isnot a simple straight channel, and is not a gate at the start of achannel.

A “footer” is a manifold arranged to take away fluid from connectingchannels.

A “gate” comprises an interface between the manifold and two or moreconnecting channels. A gate has a nonzero volume. A gate controls flowinto multiple connecting channels by varying the cross sectional area ofthe entrance to the connecting channels. A gate is distinct from asimple orifice, in that the fluid flowing through a gate has positivemomentum in both the direction of the flow in the manifold and thedirection of flow in the connecting channel as it passes through thegate. In contrast, greater than 75% of the positive momentum vector offlow through an orifice is in the direction of the orifice's axis. Atypical ratio of the cross sectional area of flow through a gate rangesbetween 2-98% (and in some embodiments 5% to 52%) of the cross sectionalarea of the connecting channels controlled by the gate including thecross sectional area of the walls between the connecting channelscontrolled by the gate. The use of two or more gates allows use of themanifold interface's cross sectional area as a means of tailoringmanifold turning losses, which in turn enables equal flow rates betweenthe gates. These gate turning losses can be used to compensate for thechanges in the manifold pressure profiles caused by friction pressurelosses and momentum compensation, both of which have an effect upon themanifold pressure profile. The maximum variation in the cross-sectionalarea divided by the minimum area, given by the Ra number, is preferablyless than 8, more preferably less than 6 and in even more preferredembodiments less than 4.

In a preferred shim construction (shown in FIGS. 3E and 3F), a gatecomprises two or more adjoining shims that have channel walls 32′connected at their respective ends. These end wall connections 34′ fixthe channel walls in space so that the ends do not move duringmanufacturing and handling. At least one shim has end wall connectionscontinuous across the width of the gate's two or more connectingchannels and walls to form the perimeter edge of the manifold 34′. Theend wall connection in this shim creates a barrier for fluid flowbetween the manifold 36 and the two or more connecting channels 35′. Theillustrated shim also has an intermediate wall connection 37′ betweenthe connecting channels and the end wall connections. The planeextending in the stacking direction from wall 37′ is the connectingchannel plane exit or entrance. The intermediate wall connection acts asa barrier for flow between the gate's two or more connecting channels,leaving an open volume between connections for flow distribution in theconnection 38′. At least one other shim (the “gate opening” shim) has,where it interfaces the manifold perimeter, the end wall connection 42′only partially continuous across the width of the gate's two or moreconnecting channels and walls. There is one continuous section 44′ ofthe end wall channel that is offset from the manifold perimeter,extending from the manifold 36′ far enough to allow a flow to travelpast the barrier created by the continuous end wall connections. Thewalls 44′ and 34′ form a connection 46′ between the manifold and theconnecting channels. The plane extending in the stacking direction fromwall 34′ is the manifold interface plane. Two or more connectingchannels in the “gate opening” shim provide a flow connection 46′ intothe connecting channels.

In some preferred embodiments, connecting channels are aligned inadjacent shims (such as in region 47′ of FIG. 3E)

A “grate” is a connection between a manifold and a single channel. Agrate has a nonzero connection volume. In a shim construction (shown inFIG. 3D), a grate is formed when a cross bar in a first shim is notaligned with a cross bar in an adjacent second shim such that flowpasses over the cross bar in the first shim and under the cross bar inthe second shim.

The “head” refers to the dynamic head of a channel flow, defined by thefollowing equation,

$\begin{matrix}{{head} = {\frac{\rho \; U^{2}}{2} = \frac{G^{2}}{2\rho}}} & (3)\end{matrix}$

whereρ [kg/m3]=density of the fluidG [kg/m2/s]=mass flux rate of the fluidU [m/s]=specific velocity of the fluidThe head is defined at the position of interest.

A “header” is a manifold arranged to deliver fluid to connectingchannels.

A “height” is a direction perpendicular to length. In a laminateddevice, height is the stacking direction. See also FIG. 1A.

A “hydraulic diameter” of a channel is defined as four times thecross-sectional area of the channel divided by the length of thechannel's wetted perimeter.

An “L-manifold” describes a manifold design where flow direction intoone manifold is normal to axes of the connecting channel, while the flowdirection in the opposite manifold is parallel with the axes of theconnecting channels. For example, a header L-manifold has a manifoldflow normal to the axes of the connecting channels, while the footermanifold flow travels in the direction of connecting channels axes outof the device. The flow makes an “L” turn from the manifold inlet,through the connecting channels, and out of the device. When twoL-manifolds are brought together to serve a connecting channel matrix,where the header has inlets on both ends of the manifold or a footer hasexits from both ends of the manifold, the manifold is called a“T-manifold”.

A “laminated device” is a device made from laminae that is capable ofperforming a unit operation on a process stream that flows through thedevice.

A “length” refers to the distance in the direction of a channel's (ormanifold's) axis, which is in the direction of flow.

“M2M manifold” is defined as a macro-to-micro manifold, that is, amicrochannel manifold that distributes flow to or from one or moreconnecting microchannels. The M2M manifold in turn takes flow to or fromanother larger cross-sectional area delivery source, also known as macromanifold. The macro manifold can be, for example, a pipe, a duct or anopen reservoir.

A “macromanifold” is a pipe, tube, or duct that connects multiplemicrodevices to a single inlet and/or outlet. Flow in the macromanifoldis in either the transition or turbulent regime. Each microdevicefurther comprises a manifold for distributing flow to multiple parallelmicrochannels (i.e., a connecting channel matrix).

A “manifold” is a volume that distributes flow to two or more connectingchannels or to a very large aspect ratio (aspect ratios >30:1) singleconnecting channel. Aspect ratio is defined as the width of the channel(the flow direction through the volume) over its height in the stackingdirection. The entrance, or inlet, plane of a header manifold is definedas the plane in which marks a significant difference in header manifoldgeometry from the upstream channel. The header manifold includes anyvolume between the entrance plane and the LM2M header beginning point.The exit, or outlet, plane of the footer manifold is defined as theplane which marks a significant difference in the footer manifoldchannel from the downstream channel. A significant difference inmanifold geometry will be accompanied by a significant difference inflow direction and/or mass flux rate. A manifold includes submanifoldsif the submanifolding does not cause significant difference in flowdirection and/or mass flux rate. The footer manifold includes any volumebetween the LM2M footer end point and the exit plane. For example, amicrochannel header manifold's entrance plane is the plane where themicrochannel header interfaces a larger delivery header manifold, suchas a pipe or duct, attached to the microchannel device through welding aflange or other joining methods. Similarly, a header manifold starts atthe plane where a tub-like, non-microchannel header connects with amicrochannel header space. In most cases, a person skilled in this artwill readily recognize the boundaries of a manifold that serves a groupof connecting channels.

A “manifold connection” is the plane between the manifold and one ormore connecting channels. The manifold connection plane can have avolume associated with it for a single connecting channel, and must havea volume if connected through a gate to two or more channels.

A “manifold length” (LM2M) is the length of the manifold over itsconnecting channels. For a header, LM2M is the distance between wherethe wall plane closest to the header entrance belonging to theconnecting channel closest to the header entrance connects with themanifold channel axis, the “LM2M header beginning point”, and theposition where the wall plane farthest away from the header entrancebelonging to the connecting channel farthest away from the headerentrance connects with the manifold channel axis, the “LM2M header endpoint”. For a header T-manifolds and header U-manifolds, the LM2M headerend point is the midpoint on the line between the two opposite LM2Mheader beginning points if the channel has a constant cross-sectionalarea and the LM2M header end point is where the two sides's manifoldchannel axis lines cross, assuming symmetry between the two manifoldsides. For a footer, the LM2M is the distance between the position wherethe wall plane farthest away from the footer exit belonging to theconnecting channel farthest away from the footer exit connects with thechannel axis, the “LM2M footer beginning point”, and the position wherethe wall plane closest to the footer exit belonging to the connectingchannel closest to the footer exit connects with the channel axis, the“LM2M footer end point”. For a header T-manifolds and headerU-manifolds, the LM2M header end point is the midpoint on the linebetween the two opposite LM2M header beginning points if the channel hasa constant cross-sectional area and the LM2M header end point is wherethe two sides's manifold channel axis lines cross, assuming symmetrybetween the two manifold sides. An example of LM2M is seen in FIG. 1A1.

For a header the “manifold pressure drop” (DPmanifold) is the staticpressure difference between the arithmetic mean of the area-averagedcenter pressures of the header manifold inlet planes (in the case wherethere is only one header inlet, there is only one inlet plane) and thearithmetic mean of each of the connecting channels' entrance planecenter pressures. The header manifold pressure drop is based on theheader manifold entrance planes that comprise 95% of the net flowthrough the connecting channels, the header manifold inlet planes havingthe lowest flow are not counted in the arithmetic mean if the flowthrough those header manifold inlet planes is not needed to account for95% of the net flow through the connecting channels. The header (orfooter) manifold pressure drop is also based only on the connectingchannels' entrance (or exit) plane center pressures that comprise 95% ofthe net flow through the connecting channels, the connecting channels'entrance (or exit) planes having the lowest flow are not counted in thearithmetic mean if the flow through those connecting channels is notneeded to account for 95% of the net flow through the connectingchannels. For a footer, the manifold pressure drop is the staticpressure difference between the arithmetic mean of each of theconnecting channel's exit plane center pressures and the arithmetic meanof the area-averaged center pressures of the footer manifold outletplanes (in the case where there is only one header outlet, there is onlyone outlet plane). The footer manifold pressure drop is based on thefooter manifold exit planes that comprise 95% of the net flow throughthe connecting channels, the footer manifold outlet planes with thelowest flow are not counted in the arithmetic mean if the flow throughthose exit planes is not needed to account for 95% of the net flowthrough the connecting channels.

For a header manifold the “manifold to interface pressure drop” (DPM2I)is the static pressure difference between the point of the “headermanifold pressure at the interface”, where the header manifold channelaxis crosses the plane that bisects the manifold connection widththrough the manifold connection channel axis, where that plane goesthrough the bottom and top of the manifold connection channel in thestacking direction, and the center of the connecting channel inlet planeor the arithmetic mean of the connecting channel plane centers connectedto the manifold connection. For a footer manifold the manifold tointerface pressure (i.e., the “footer manifold pressure at theinterface”) is defined as the absolute value of the pressure differencebetween the arithmetic mean of the connecting channel's exit planecenter pressures and the point where the footer manifold channel axiscrosses the plane that bisects the manifold connection width through themanifold connection axis, where that plane goes through the bottom andtop of the manifold connection channel in the height (stacking forlaminated device) direction. Examples of the manifold connection includea grate, a gate or orifices. The manifold connection can only be theentrance or exit of a connecting channel if the manifold connection is aplane between the connection and the manifold.

The mass flux rate G is the mass flow rate per unit cross-sectional areaof the channel in the direction of the channel's axis.

The ratio of the manifold's head to its friction loss, Mo, is defined bythe following equation:

$\begin{matrix}{{Mo} = {\frac{\frac{1}{2\rho}\left\lbrack {G^{2} - 0} \right\rbrack}{\frac{4{fL}_{M\; 2M}}{D}\frac{G^{2}}{2\rho}} = \left\{ \frac{4{fL}_{M\; 2M}}{D} \right\}^{- 1}}} & (4)\end{matrix}$

where,D [m]=manifold hydraulic diameter at the M2M reference pointf [dimensionless]=Fanning friction factor for the M2M reference pointG [kg/m2/s]=mass flux rate at the M2M reference point

The reference point of header manifold Reynolds number and hydraulicdiameter for Mo are defined at the position on the channel axis wherethe wall plane closest to the header entrance belonging to theconnecting channel closest to the entrance in the manifold connects withthe channel axis. The footer manifold Reynolds number and hydraulicdiameter for Mo are defined at the reference point at the position wherethe wall plane closest to the footer exit belonging to the connectingchannel closest to footer exit connects with the channel axis.

A “module” is a large capacity microchannel device, made up of multiplelayers of repeating unit combinations.

An “open channel” is a gap of at least 0.05 mm that extends all the waythrough a microchannel such that fluids can flow through themicrochannel with relatively low pressure drop.

The “pressure drop ratio #1” (PDR1) is defined as the ratio ofconnecting channel pressure drop over the representative head of themanifold (the LM2M header beginning point″ for a header, the LM2M footerend point″ for the footer):

$\begin{matrix}{{DPR}_{1} = {\frac{\Delta \; P_{CCdP}}{h} = \frac{\Delta \; P_{CCdP}}{\frac{G^{2}}{2\rho}}}} & (5)\end{matrix}$

If a manifold has more than one sub-manifold, the head is based upon thearithmetic (number average) mean of the individual sub-manifold G and rvalues.

The “pressure drop ratio #2” (PDR2) is defined as the ratio ofconnecting channel pressure drop over the manifold pressure drop:

$\begin{matrix}{{DPR}_{2} = \frac{\Delta \; P_{CCdP}}{\Delta \; P_{manifold}}} & (6)\end{matrix}$

If a manifold has more than one sub-manifold, the manifold pressure dropis based upon the number average of sub-manifold values.

The “pressure drop ratio #3” (DPR3) is defined as the ratio of manifoldto interface pressure drop over the manifold pressure drop,

$\begin{matrix}{{DPR}_{3} = \frac{\Delta \; P_{M\; 2I}}{\Delta \; P_{manifold}}} & (7)\end{matrix}$

In preferred embodiments, the arithmetic mean of DPR3 for a manifold isless than 0.9, based on the manifold connections that comprise 95% ofthe net flow through the connecting channels, the lowest flow manifoldconnections are not counted if the flow through those channels is notneeded to account for 95% of the net flow through the connectingchannels. More preferable embodiments have DPR3 values based on the samecriteria of less than 0.75, more preferably less than 0.50, morepreferably still 0.25 and most preferably less than 0.10.

“Process channel volume” is the internal volume of a process (i.e.,connecting) channel. This volume includes the volume of the catalyst (ifpresent) and the open flow volume (if present). This volume does notinclude the channel walls. For example, a reaction chamber that iscomprised of a 2 cm×2 cm×0.1 cm catalyst and a 2 cm×2 cm×0.2 cm openvolume for flow immediately adjacent to the catalyst, would have a totalvolume of 1.2 cm3.

Quality Index factor “Q1” is a measure of how effective a manifold is indistributing flow. It is the ratio of the difference between the maximumand minimum rate of connecting channel flow divided by the maximum rate.For systems of connecting channels with constant channel dimensions itis often desired to achieve equal mass flow rate per channel. Theequation for this case is shown below, and is defined as Q1.

$\begin{matrix}{Q_{1} = {\frac{m_{\max} - m_{\min}}{m_{\max}} \times 100\%}} & (8)\end{matrix}$

wherem_(max) [kg/sec]=maximum connecting channel mass flow ratem_(min) [kg/sec]=minimum connecting channel mass flow rateFor cases when there are varying connecting channel dimensions it isoften desired that the residence time, contact time, velocity or massflux rate have minimal variation from channel to channel such that therequired duty of the unit operation is attained. For those cases wedefine a quality index factor Q2:

${Q_{2} = {\frac{G_{\max} - G_{\min}}{G_{\max}} \times 100\%}},$

where G is the mass flux rate. For cases when all the connectingchannels have the same cross sectional area, the equation for Q2simplifies to Q1. The quality index factor gives the range of connectingchannel flow rates, with 0% being perfect distribution, 100% showingstagnation (no flow) in at least one channel, and values of over 100%indicating backflow (flow in reverse of the desired flow direction) inat least one channel. For the examples, Q1 and Q2 are unadjusted;however, in the claims, Q1 and Q2 are defined based on the channels thatcomprise 95% of the net flow through the connecting channels, the lowestflow channels are not counted if the flow through those channels is notneeded to account for 95% of the net flow through the connectingchannels.

Ra (=Amax/Amin) is the cross-sectional area ratio of the biggest to thesmallest connection between a manifold and connecting channels. Theseareas can belong to gates or grates.

The Reynolds number, Re, is the commonly used ratio of the inertial overthe viscous forces seen by flow in a channel. Its definition is theratio of the mass flux rate (G) times the hydraulic diameter (D) dividedby the dynamic viscosity (m),

$\begin{matrix}{{Re} = {\frac{GD}{\mu} = \frac{\rho \; {UD}}{\mu}}} & (9)\end{matrix}$

The value of the Reynolds number describes the flow regime of thestream. While the dependence of the regime on Reynolds number is afunction of channel cross-section shape and size, the following rangesare typically used for channels:

Laminar: Re<2000 to 2200 Transition: 2000-2200<Re<4000 to 5000Turbulent: Re>4000 to 5000

“Sheets” or “shims” refer to substantially planar plates or sheets thatcan have any width and length and preferably have a thickness (thesmallest dimension) of 5 millimeter (mm) or less, more preferably 0.080inch (2 mm) or less, and in some preferred embodiments between 50 and1000 μm. Width and length are mutually perpendicular and areperpendicular to thickness. In preferred embodiments, a sheet has lengthand width that are coextensive the length and width of the stack oflaminae in which the sheet resides. Length of a sheet is in thedirection of flow; however, in those cases in which the direction offlow cannot be determined, length is the longest dimension of a sheet.

A “subchannel” is a channel that is within a larger channel. Channelsand subchannels are defined along their length by channel walls.

A “sub-manifold” is a manifold that operates in conjunction with atleast one other submanifold to make one large manifold in a plane.Sub-manifolds are separated from each other by continuous walls.

“Thickness” is measured in the stacking direction.

In a “U-manifold,” fluid in a header and footer flow in oppositedirections while being at a non zero angle to the axes of the connectingchannels. When two U-manifolds are brought together to serve aconnecting channel matrix, with entrances on both open ends of theheader manifold and exits on both open ends of the footer, the manifoldis called an “I-manifold”.

“Unit operation” means chemical reaction, vaporization, compression,chemical separation, distillation, condensation, mixing, heating, orcooling. A “unit operation” does not mean merely fluid transport,although transport frequently occurs along with unit operations. In somepreferred embodiments, a unit operation is not merely mixing.

In a “Z-manifold,” fluid in a header and footer flow in the samedirection while being at a non zero angle to the axes of the connectingchannels. Fluid entering the manifold system exits from the oppositeside of the device from where it enters. The flow essentially makes a“Z” direction from inlet to outlet.

A first aspect of the present invention is illustrated in exemplary formin FIGS. 3-11. Referring to FIG. 3, the process is operated usingmicrochannel reactor 100 which includes microchannel reactor core 102,process feed stream header 104, staged addition feed stream header 106,product footer 108, heat exchange header 110, heat exchange footer 112,and manifold and recuperator 116. A process feed stream comprising O₂ orH₂ flows into the microchannel reactor 100 through the process feedstream header 104, as indicated by directional arrow 118. A stagedaddition feed stream comprising O₂ or H₂ flows into the microchannelreactor 100 through the staged addition feed stream header 106, asindicated by directional arrow 120. It will be understood by thoseskilled in the art that when the process feed stream comprises O₂, thestaged addition feed stream will comprise H₂. Alternatively, when theprocess feed stream comprises H₂, the staged addition feed stream willcomprise O₂. The process feed stream and the staged addition feed streamflow into and through the manifold and recuperator 116 into the reactorcore 102 wherein they are mixed with each other in one or more processmicrochannels to form a reactant mixture comprising O₂ and H₂. Thereactant mixture contacts a catalyst within the one or more processmicrochannels and is converted to a product comprising hydrogenperoxide. The product flows from the reactor core 102 through themanifold and recuperator 116 to product footer 108, and from productfooter 108 out of the reactor, as indicated by directional arrow 122.Although an advantage of the inventive process is that a high level ofconversion of O₂ and/or H₂ may be obtained with one pass through themicrochannel reactor, in one embodiment, unreacted O₂ and/or H₂ may beseparated from the product using conventional techniques and recycledback through the microchannel reactor. The unreacted O₂ and/or H₂ may berecycled through the microchannel reactor any number of times, forexample, one, two, three, four times, etc. A heat exchange fluid flowsinto heat exchange header 110, as indicated by directional arrow 124,and from heat exchange header 110 through the reactor core 102 to heatexchange footer 112, and out of heat exchange footer 112, as indicatedby directional arrow 126. Heat exchange between the feed and productstreams and the heat exchange fluid may be effected using convectiveheat transfer. In one exemplary embodiment, heat exchange may beenhanced by the heat exchange fluid undergoing a full or partial phasechange in heat exchange channels in the reactor core 102. Themicrochannel reactor 100 is employed in conjunction with storagevessels, pumps, valves, flow control devices, and the like, which arenot shown in the drawings, but would be apparent to those skilled in theart.

The process feed stream and the staged addition feed stream are mixedwith each other in the one or more process microchannels in themicrochannel reactor. In one embodiment, the catalyst is positionedwithin a reaction zone in the one or more process microchannels and thestaged addition feed stream is mixed with the process feed stream in thereaction zone. In one exemplary embodiment, the one or more processmicrochannels contain a mixing zone and a reaction zone, the mixing zonebeing positioned upstream of the reaction zone, the catalyst beingpositioned in the reaction zone, and the staged addition feed stream ismixed with the process feed stream in the mixing zone. In a furtherexemplary embodiment, the one or more process microchannels contain amixing zone and a reaction zone, and the process feed stream and thestaged addition feed stream are partially mixed in the mixing zone andpartially mixed in the reaction zone. In still a further exemplaryembodiment, from about 1% to about 99% by volume of the staged additionfeed stream is mixed with the process feed stream in the mixing zone andthe remainder of the staged addition feed stream is mixed with theprocess feed stream in the reaction zone. The volume of the stagedaddition feed stream that is mixed with the process feed stream in themixing zone may range from about 5% to about 95% by volume, and in oneembodiment from about 10% to about 90% by volume, and in one embodimentfrom about 20% to about 80% by volume, and in one embodiment from about30% to about 70% by volume, and in one embodiment from about 40% toabout 60% by volume, with the remainder of the staged addition feedstream being mixed with the process feed stream in the reaction zone.

The mixing of the O₂ and H₂ in the one or more process microchannels ofthe microchannel reactor provides the advantage of safe handling of thereactants, as will be discussed in further detail herein.

FIG. 4 illustrates repeating unit 130 which may be used in the reactorcore 102 of the microchannel reactor 100. Repeating unit 130 is housedwithin housing unit 132. The inventive process is conducted usingprocess microchannels 140 and 150, staged addition microchannel 160,orifices 170, and heat exchange channels 180 and 190. The process feedstream comprising O₂ or H₂ flows through process microchannels 140 and150, as indicated by the directional arrows 141 and 151, respectively.The staged addition feed stream comprising H₂ or O₂ flows through thestaged addition microchannel 160 into orifices 170, and from theorifices 170 into process microchannels 140 and 150, as indicated bydirectional arrows 161. The process microchannels 140 and 150 havemixing zones 142 and 152, respectively, wherein the process feed streamand staged addition feed stream contact each other and form a reactantmixture comprising O₂ and H₂. The process microchannels 140 and 150 alsohave reaction zones 143 and 153, respectively, wherein the catalyst ispresent and the reactant mixture contacts the catalyst and reacts toform a product comprising hydrogen peroxide. The mixing zones 142 and152 are positioned upstream from the reaction zones 143 and 153,respectively. The product exits the process microchannels 140 and 150,as indicated by the directional arrows 144 and 154, respectively. Theproduct exiting the process microchannels 140 and 150 flows to themanifold and recuperator 116, and from the manifold and recuperator 116through the product footer 108 and out of the reactor, as indicated byarrow 122. Heat exchange fluid flows from heat exchange header 110through heat exchange channels 180 and 190, as indicated by directionalarrows 181, and 191 and 192, respectively, to heat exchange footer 112.The flow of heat exchange fluid in the direction indicated by arrows181, 191 and 192 is cross-current to the flow of fluid flowing throughprocess microchannels 140 and 150 as indicated by arrows 141 and 151,respectively. Alternatively, the heat exchange channels 180 and 190could be oriented to provide for the flow of the heat exchange fluid ina direction that would be cocurrent or counter-current to the flow offluid through the process microchannels 140 and 150. The repeating unit130 illustrated in FIG. 4 may occur once within the microchannel reactorcore 102 or it may be repeated any number of times, for example, two,three, four, five, ten, twenty, fifty, one hundred, hundreds, onethousand, thousands, ten thousand, tens of thousands, one hundredthousand, hundreds of thousands or millions of times.

FIG. 5 illustrates another exemplary repeating unit 230 which may beused in the reactor core 102 of the microchannel reactor 100. Theinventive process is conducted using process microchannel 240, stagedaddition microchannel 260, orifices 270, and heat exchange channel 280.Process microchannel 240 has a reaction zone 242, wherein the catalystis present. The process feed stream comprising O₂ or H₂ flows throughprocess microchannel 240, as indicated by the directional arrow 241. Thestaged addition feed stream comprising H₂ or O₂ flows through the stagedaddition microchannel 260 into and through the orifices 270, and fromthe orifices 270 into the reaction zone 242 as indicated by directionalarrows 261. In the reaction zone 242 the staged addition feed streammixes with the process feed stream to form a reactant mixture comprisingO₂ and H₂. The reactant mixture contacts the catalyst and reacts to forma product comprising hydrogen peroxide. The product exits the processmicrochannel 240, as indicated by the directional arrow 244. The productexiting the process microchannel 240 flows to the manifold andrecuperator 116, and from the manifold and recuperator 116 through theproduct footer 108 and out of the reactor, as indicated by arrow 122.Heat exchange fluid flows from heat exchange header 110 through heatexchange channel 280, as indicated by directional arrows 281, to heatexchange footer 112. The flow of heat exchange fluid in the directionindicated by arrows 281 is counter-current to the flow of fluid flowingthrough process microchannel 240. Alternatively, the heat exchangechannel 280 could be oriented to provide for the flow of the heatexchange fluid in a direction that would be cocurrent or cross-currentto the flow of fluid through the process microchannel 240. The repeatingunit 230 illustrated in FIG. 5 may occur once within the microchannelreaction zone 114 or it may be repeated any number of times, forexample, two, three, four, five, ten, twenty, fifty, one hundred,hundreds, one thousand, thousands, ten thousand, tens of thousands, onehundred thousand, hundreds of thousands or millions of times.

FIG. 6 illustrates a further exemplary repeating unit 330 which may beused in the reactor core 102 of the microchannel reactor 100. Theinventive process is conducted using process microchannels 340 and 350,staged addition microchannel 360, orifices 370, and heat exchangechannels 380 and 390. The process microchannels 340 and 350 have mixingzones 342 and 352, respectively, and reaction zones 343 and 353,respectively. The catalyst is present in the reaction zones 343 and 353.The mixing zones 342 and 352 are positioned upstream of the reactionzones 343 and 353. The process feed stream comprising O₂ or H₂ flowsthrough process microchannels 340 and 350, as indicated by thedirectional arrows 341 and 351, respectively. The staged addition feedstream comprising H₂ or O₂ flows through the staged additionmicrochannel 360 into and through orifices 370, and from the orifices370 into process microchannels 340 and 350, as indicated by directionalarrows 361. In the process microchannels 340 and 350 a portion of thestaged addition feed stream contacts and intermixes with the processfeed stream in the mixing zones 342 and 352, respectively, with theresult being the formation of a reactant mixture. This reactant mixtureflows into the reaction zones 343 and 353. The remainder of the stagedaddition feed stream contacts and intermixes with the process feedstream in the reaction zones 343 and 353, respectively, to form anadditional amount of reactant mixture. The reactant mixture comprises O₂and H₂. The reactant mixture contacts the catalyst in the reaction zones343 and 353 and reacts to form a product comprising hydrogen peroxide.The product exits the process microchannels 340 and 350, as indicated bythe directional arrows 344 and 354, respectively. The product exitingthe process microchannels 340 and 350 flows to the manifold andrecuperator 116, and from the manifold and recuperator 116 through theproduct footer 108 and out of the reactor, as indicated by arrow 122.Heat exchange fluid flows from heat exchange header 110 through heatexchange channels 380 and 390, as indicated by directional arrows 381and 391, respectively, to heat exchange footer 112. The flow of heatexchange fluid in the direction indicated by arrows 381 and 391 iscounter-current to the flow of fluid flowing through processmicrochannels 340 and 350. Alternatively, the heat exchange channels 380and 390 could be oriented to provide for the flow of the heat exchangefluid in a direction that would be cocurrent or cross-current to theflow of fluid through the process microchannels 340 and 350. Therepeating unit 330 illustrated in FIG. 6 may occur once within themicrochannel reactor core 102 or it may be repeated any number of times,for example, two, three, four, five, ten, twenty, fifty, one hundred,hundreds, one thousand, thousands, ten thousand, tens of thousands, onehundred thousand, hundreds of thousands or millions of times.

FIG. 7 illustrates still a further exemplary repeating unit 430 whichmay be used in the reactor core 102 of the microchannel reactor 100. Theinventive process is conducted using process microchannels 440, 450 and455, staged addition microchannels 460 and 465, orifices 470 and 475,and heat exchange channels 480 and 490. The process microchannels 440,450, 455 have mixing zones 442, 452 and 456, respectively, and reactionzones 443, 453 and 457, respectively. The catalyst is positioned in thereaction zones. The mixing zones are upstream from reaction zones. Theprocess feed stream comprising O₂ or H₂ flows through processmicrochannels 440 and 450, as indicated by the directional arrows 441and 451, respectively. The staged addition feed stream comprising H₂ orO₂ flows through the staged addition microchannel 460 into and throughorifices 470, and from the orifices 470 into process microchannels 440and 450, s indicated by directional arrows 461. In the processmicrochannels 440 and 450 a portion of the staged addition feed streamcontacts and intermixes with the process feed stream in the mixing zones442 and 452, respectively. The reactant mixture formed in the mixingzones 442 and 452 flows into the reaction zones 443 and 453,respectively. The remainder of the staged addition feed stream contactsand intermixes with the process feed stream in the reaction zones 443and 453, respectively, to form an additional amount of reactant mixture.The reactant mixture comprises O₂ and H₂. In the reaction zones 443 and453 the reactant mixture contacts the catalyst and reacts to form aproduct comprising hydrogen peroxide. The process feed stream also flowsthrough process microchannel 455, as indicated by directional arrow 458.The staged addition feed stream also flows through the staged additionmicrochannel 465 into and through orifices 475, and from orifices 475into process microchannel 455 as indicated by directional arrows 466. Inthe process microchannel 455 a portion of the staged addition feedstream contacts and intermixes with the process feed stream in themixing zone 456 to form a reactant mixture. The reactant mixture formedin the mixing zone 456 flows into the reaction zone 457. The remainderof the staged addition feed stream flowing through the orifices 475contacts and intermixes with the process feed stream to form a reactantmixture in the reaction zone 457. The reactant mixture comprises O₂ andH₂. In the reaction zone 457 the reactant mixture contacts the catalystand reacts to form a product comprising hydrogen peroxide. The productexits the process microchannels 440, 450 and 455 as indicated by thedirectional arrows 444, 454 and 459, respectively. The product exitingthe process microchannels 440, 450 and 455 flows to the manifold andrecuperator 116, and from the manifold and recuperator 116 through theproduct footer 108 and out of the reactor, as indicated by arrow 122.Heat exchange fluid flows from heat exchange header 110 through heatexchange channels 480 and 490, as indicated by directional arrows 481and 491, respectively, to heat exchange footer 112. The flow of heatexchange fluid in the direction indicated by arrows 481 and 491 iscounter-current to the flow of fluid flowing through processmicrochannels 440, 450 and 455. Alternatively, the heat exchangechannels 480 and 490 could be oriented to provide for the flow of theheat exchange fluid in a direction that would be cocurrent orcross-current to the flow of fluid through the process microchannels440, 450 and 455. The repeating unit 430 illustrated in FIG. 7 may occuronce within the microchannel reactor core 102 or it may be repeated anynumber of times, for example, two, three, four, five, ten, twenty,fifty, one hundred, hundreds, one thousand, thousands, ten thousand,tens of thousands, one hundred thousand, hundreds of thousands ormillions of times.

FIG. 8 illustrates an even further exemplary repeating unit 530 whichmay be used in the reactor core 102 of the microchannel reactor 100. Theinventive process is conducted using process microchannels 540 and 550,staged addition microchannels 560 and 565, orifices 570 and 575, andheat exchange channels 580 and 590. The process microchannels 540 and550 have mixing zones 542 and 552, respectively, and a common reactionzone 554. The catalyst is positioned in the reaction zone 554. Themixing zones are upstream from the reaction zone. The process feedstream comprising O₂ or H₂ flows through process microchannels 540 and550, as indicated by the directional arrows 541 and 551, respectively.The staged addition feed stream comprising H₂ or O₂ flows through thestaged addition microchannels 560 and 565 into orifices 570 and 575,respectively, and from the orifices 570 and 575 into the mixing zones542 and 552, respectively, as indicated by directional arrows 561 and566 where it mixes with the process feed stream to form a reactantmixture comprising H₂ and O₂. The reactant mixture flows into thereaction zone 554, as indicated by arrows 553, contacts the catalyst andreacts to form a product comprising hydrogen peroxide. The product exitsreaction zone 554, as indicated by the directional arrow 555. Theproduct exiting the reaction zone 554 flows to the manifold andrecuperator 116, and from the manifold and recuperator 116 through theproduct footer 108 and out of the reactor, as indicated by arrow 122.Heat exchange fluid flows from heat exchange header 110 through heatexchange channels 580 and 590, as indicated by directional arrows 581and 591 to heat exchange footer 112. The flow of heat exchange fluid inthe direction indicated by arrows 581 and 591 is counter-current to theflow of fluid flowing through process microchannels 540 and 550.Alternatively, the heat exchange channels 180 and 190 could be orientedto provide for the flow of the heat exchange fluid in a direction thatwould be cocurrent or cross-current to the flow of fluid through theprocess microchannels 540 and 550. The repeating unit 530 illustrated inFIG. 8 may occur once within the microchannel reactor core 102 or it maybe repeated any number of times, for example, two, three, four, five,ten, twenty, fifty, one hundred, hundreds, one thousand, thousands, tenthousand, tens of thousands, one hundred thousand, hundreds of thousandsor millions of times.

FIG. 9 illustrates an additional exemplary repeating unit 630 which maybe used in the reaction zone 114 of the microchannel reactor 100. Theinventive process is conducted using process microchannels 640 and 650,staged addition microchannels 660 and 665, orifices 670 and 675, andheat exchange channels 680, 685, 690 and 695. The process microchannels640 and 650 have mixing zones 642 and 652, respectively, and a commonreaction zone 654. The catalyst is positioned within the reaction zone654. The mixing zones are upstream from the reaction zone. The processfeed stream comprising O₂ or H₂ flows through process microchannels 640and 650, as indicated by the directional arrows 641 and 651,respectively. The staged addition feed stream comprising H₂ or O₂ flowsthrough the staged addition microchannels 660 and 665 into orifices 670and 675, respectively, and from the orifices 670 and 675 into the mixingzones 642 and 652, respectively, as indicated by directional arrows 661and 666. In the mixing zones 642 and 652 the staged addition feed streammixes with the process feed stream to form a reactant mixture comprisingH₂ and O₂. The reactant mixture flows into the reaction zone 654, asindicated by arrows 653, contacts the catalyst and reacts to form aproduct comprising hydrogen peroxide. The product exits the reactionzone 654, as indicated by directional arrow 655. The product exiting thereaction zone 654 flows to the manifold and recuperator 116, and fromthe manifold and recuperator 116 through the product footer 108 and outof the reactor, as indicated by arrow 122. Heat exchange fluid flowsfrom heat exchange header 110 through heat exchange channels 680 and685, and 690 and 695, as indicated by directional arrows 681 and 686,and 691 and 696, respectively, to heat exchange footer 112. The flow ofheat exchange fluid in the direction indicated by arrows 681 and 686,and 691 and 696, is cocurrent and counter-current to the flow of fluidflowing through process microchannels 640 and 650. Alternatively, theheat exchange channels 681 and 686, and 691 and 696, could be orientedto provide for the flow of the heat exchange fluid in a direction thatwould be cross-current to the flow of fluid through the processmicrochannels 640 and 650. The repeating unit 630 illustrated in FIG. 9may occur once within the microchannel reactor core 102 or it may berepeated any number of times, for example, two, three, four, five, ten,twenty, fifty, one hundred, hundreds, one thousand, thousands, tenthousand, tens of thousands, one hundred thousand, hundreds of thousandsor millions of times.

FIG. 10 illustrates a further exemplary repeating unit 730 which may beused in the reactor core 102 of the microchannel reactor 100. Theinventive process is conducted using process microchannel 740, stagedaddition microchannels 760 and 765, orifices 770 and 775, and heatexchange channels 780 and 790. The process microchannel 740 has mixingzone 742 and reaction zones 743 and 744. The catalyst is positioned inthe reaction zones 743 and 744. The mixing zone 742 is upstream from thereaction zones. The process feed stream comprising O₂ or H₂ flowsthrough process microchannel 740, as indicated by the directional arrow741. The staged addition feed stream comprising H₂ or O₂ flows throughthe staged addition microchannels 760 and 766 into orifices 770 and 775,respectively, and from the orifices 770 and 775 into the mixing zone742, as indicated by directional arrows 761 and 766. In the mixing zone742 the staged addition feed stream is mixed with the process feedstream to form a reactant mixture comprising H₂ and O₂. The reactantmixture flows into the reaction zones 743 and 744, as indicated byarrows 745, contacts the catalyst and reacts to form a productcomprising hydrogen peroxide. The product exits reaction zones 743 and744, as indicated by the directional arrows 746 and 747, respectively.The product exiting the reaction zone 743 and 744, flows to the manifoldand recuperator 116, and from the manifold and recuperator 116 throughthe product footer 108 and out of the reactor, as indicated by arrow122. Heat exchange fluid flows from heat exchange header 110 throughheat exchange channels 780 and 790, as indicated by directional arrows781 and 791, to heat exchange footer 112. The flow of heat exchangefluid in the direction indicated by arrows 781 and 791 is co-current tothe flow of fluid flowing through the reaction zones 743 and 744.Alternatively, the heat exchange channels 780 and 790 could be orientedto provide for the flow of the heat exchange fluid in a direction thatwould be counter-current or cross-current to the flow of fluid throughthe reaction zones 743 and 744. The repeating unit 730 illustrated inFIG. 10 may occur once within the microchannel reactor core 102 or itmay be repeated any number of times, for example, two, three, four,five, ten, twenty, fifty, one hundred, hundreds, one thousand,thousands, ten thousand, tens of thousands, one hundred thousand,hundreds of thousands or millions of times.

The repeating unit 730 a illustrated in FIG. 11 is identical to therepeating unit 730 illustrated in FIG. 10 with the exception that theorifices 770 and 775 illustrated in FIG. 10 are aligned directlyopposite each other, while the orifices 770 a and 775 a illustrated inFIG. 11 are offset from such direct alignment. In FIG. 10 the stagedaddition feed streams flowing through the orifices 770 and 775 impingedirectly on one another thereby enhancing the diffusion of such streamsin the mixing zone 742. On the other hand, in FIG. 11 the stagedaddition feed streams flowing through the orifices 770 a and 775 aalternate in sequence to reduce the diffusional distance between thecenterlines of the process feed stream and the staged addition feedsteam.

The contacting time for post orifice mixing may be defined, for example,with reference to FIG. 10 or 11, using the sum of the total of the flowthrough the orifices 770 and 775 (or 770 a and 775 a) and the flow ofthe process feed stream in process microchannel 740, as indicated byarrow 741, at standard conditions of temperature (i.e., 20 C) andpressure (i.e., atmospheric pressure), and the volume defined by theprocess microchannel 740 between the tangent of the last orifices 770and 775 (or 770 a and 775 a) (downstream of the flow of the process feedstream) and the beginning of the catalysts in the reaction zones 743 and744. This contacting time may range of about 0.25 ms to about 500 ms,and in one embodiment from about 0.25 ms to about 250 ms, and in oneembodiment from about 0.25 to about 50 ms, and in one embodiment fromabout 0.25 to about 2.5 ms.

Referencing FIG. 12, an alternate exemplary embodiment of the presentinvention 10 includes one or more microchannels 12 carrying a mixture ofwater 14 and a hydrogen source 16 (such as hydrogen gas or a chemicaloperative to donate an atom or hydrogen ion). For purposes ofexplanation only, the hydrogen source 16 shall be explained withreference to hydrogen or hydrogen gas. The microchannels 12 carrying amixture of water 14 and hydrogen 16 are in fluid communication with oneor more microchannels 18 comprising the mixing zone 20. The mixing zone20 includes those areas where oxygen or air or another oxidant 22 beingfed by one or more channels 24 is mixed with the water 14 and hydrogen16 stream. It is to be understood that further mixing of the water 14,hydrogen source 16, and oxidant 22 may take place within the reactionzone (catalyst zone) 26 of one or more channels 28 or directly upstreamof the catalyst. Hydrogen peroxide 30 is produced from a number ofexothermic reactions within the reaction zone 26 between the water 14,hydrogen 16, and oxidant 22. Thermal energy removal may occur primarilythrough convective heat transfer of a gas or liquid or through full orpartial boiling of a fluid such as water or oil (represented by stream32) that is in thermal communication with the reaction zone 26 and/or adownstream channel in fluid communication with the reaction zone 26. Itis to be understood that the pressures within the microchannels mayrange from essentially atmospheric to in excess of 50 atm.

Additional exemplary flow stream layouts are illustrated in FIGS. 13a-13 e and FIG. 14. In a first alternate exemplary flow stream layout36, as shown in FIG. 13 a, the water 14 is premixed with hydrogen 16before entering a microchannel 38 where the mixture of water 14 andhydrogen 16 mixes with oxygen 22 and reacts to produce hydrogen peroxide30 and thermal energy is drawn away from the microchannel 38 using aheat transfer stream 40 in thermal communication therewith. In a secondalternate exemplary flow stream layout 42, as shown in FIG. 13 b, themixing of water 14, hydrogen 16 and oxygen 22 all takes place within amicrochannel 44, but includes separate feed streams 46, 48 inputting thehydrogen 16 and oxygen 22, where the hydrogen 16 and water 14 mix priorto the introduction of oxygen 22. A heat transfer stream 50 is utilizedto transfer energy from the microchannel 44. A third alternate exemplaryflow stream layout 52, as shown in FIG. 13 c, is an alternate streamconfiguration to FIG. 13 b. In a fourth alternate exemplary flow streamlayout 54, as shown in FIG. 13 d, the mixing of water 14 with hydrogen16 and oxygen 22 takes place in generally the same physical locationalong the length of the microchannel 56, where a heat transfer stream 58is in thermal communication with the microchannel 56 downstream of wherethe oxygen 22 and hydrogen 16 are introduced. In a fifth alternateexemplary flow stream layout 60, as shown in FIG. 13 e, two heattransfer streams 62, 64 are in thermal communication with the processmicrochannel 66 directly downstream from the reaction zone 26. Theseheat transfer streams 62, 64 may be positioned on one side of theprocess channel 66 or on multiple sides of the process channel 66. Inaddition, these heat transfer streams 62, 64 may be shorter, the samelength, or longer than the process channel 66. In a further exemplaryflow stream layout 68, as shown in FIG. 14, a repeating unit 70 includesa heat transfer configuration 72 having an M-shaped design adapted tocarry away thermal energy from two reaction zones 26.

It is to be understood that the walls of the microchannels in theexemplary embodiments discussed herein may be coated with materials toinhibit corrosion and/or material degradation. These coatings mayinclude, without limitation, oxides such as alumina, silica, titania,chromia, zirconia, and combinations thereof, as well as metalliccoatings, including aluminum, nickel, titanium, others. Still further,these coatings may also be polymeric, including Teflon, plastics, orcombinations thereof. Application of these coatings may be applied priorto, during, or after fabrication and/or assembly of the microchannels.

In a further alternate exemplary embodiment (not shown) of the presentinvention, one or more reactant species are distributed continuouslyalong a length of a microchannel reactor. A narrow-gap continuous phasebed is utilized to prevent bubbles (gas dispersed in liquid phase) ordroplets (liquid dispersed in liquid phase) from agglomerating orcoalescing and growing in size as reactant is introduced. The walls ofthe microchannel are perforated and may be designed to possess variousopenness profiles and size distributions. This configuration providesfor fine, uniform dispersion of one phase into another that may beachieved at high holdup ratios, where the holdup ratio is generallydefined as the ratio of the volume of fluid in the dispersed phase tothe total fluid volume. High phase holdup combined with fine bubbles ordroplets leads to a greater ratio of interfacial area to unit reactorvolume. For chemical reactions between reactants in more than one phase,more interfacial area is generally operative for reaction enhancement.In addition, fine, uniform dispersion of one phase into anotherfacilitates removal or distribution of reaction heat from the generationlocations to prevent hot spots that may adversely effect selectivity.

Referring to FIG. 15, a further exemplary embodiment 801 of the presentinvention includes a microchannel device for the absorption of achemical species 821 from a gaseous or vapor stream 841 by an absorbent861 flowing within a liquid stream 881. The liquid absorbent 861 isdistributed into a series of parallel microchannels (the processmicrochannels) 901. The gas or vapor stream 841 enters a set ofmicrochannels 921 in a plane parallel to the plane in which the processmicrochannels 901 run and is introduced to the process microchannels 901either by jets, orifices, or materials 941 that produce small bubbles (ala the emulsification process). These jets, orifices or bubble formingmedia 941 may be located at any position in the microchannels 901 or maybe located just below the microchannels 901. The resultant liquid/gasmixture 961 flows up through the channels 901 and the product, in thisexemplary embodiment, hydrogen peroxide exits via a product stream 981and the gas 821 exits via a gaseous stream 1001.

Referencing FIG. 16, an additional exemplary embodiment 1101 involvesthe production of hydrogen peroxide 301 in a microchannel 1121 with asubsequent removal of the product via an absorbent liquid 1141. Thereactant mixture of hydrogen 161 and oxygen 221 and water 141 isdistributed to one or more microchannels 1121. The reactants can bepremixed or mixed in the microchannels 1121 just upstream from thecatalyst 116 or over the catalyst itself. The catalyst 1161 may bedisposed in the reactor by any means such as a wall coating, felt, foam,wad or bed of particles. Once the reaction has been completed the gasflows across a wetted wick 1181 and product is absorbed. This isespecially true in a system like hydrogen peroxide 301 production wherethe product is soluble in for example water but the hydrogen and oxygenreactants are only sparingly soluble.

Referencing FIGS. 17-20, a further detailed exemplary embodiment 1201utilizes a pressure vessel assembly 1221 to contain a reactor coolant1241. The coolant 1241 can be selected so one or more microchannelreactors 1261 can be subjected to an external compressive pressure tohelp control stresses and reduce the quantity of metal used within thereactors if that is desirable. The pressure vessel 1221 can also beconfigured to serve as a vapor/liquid separator for the heat exchangemedium 1241 in partial boiling situations. Presumably the vapor phase ofthe coolant 1241 would be routed back to a condenser (not shown) and theliquid phase would be recycled to a supply header via a cooler and pump(not shown). A positive seal between the coolant inlet 1281 anddischarge 1301 would not be required.

Referring specifically to FIGS. 17 and 18, a horizontal pressure vesselassembly 1221 illustrates a strategy for having removableco-flow/counter flow microchannel reactors 1261. The design utilizes thepresumption that the hydrogen peroxide product stays sufficientlyentrained in the bulk product stream while being routed to avapor/liquid separator (not shown). This design allows for easyreplacement of reactors 1261 if needed and easy replacement oftraditional pellet or powder catalyst forms. The flexibility of beingable to remove the reactors and orient them as needed may alsofacilitate wash coating or vacuum deposition of catalytic material orprotective coatings. Common gasket materials can be utilized on themanifold sealing surfaces to prohibit undesirable stream comingling.Traditional flanged heads could be part of the reactor assembly. Asdepicted, the process manifolding would exit through and be coupled toone reactor head—“nozzle end”. Subsequently, this reactor head will beremoved when the microchannel reactors are pulled for service. The“non-nozzle end” head could provide for general access needs such asbolting the assembly down once installed or as a means of visualinspection. If this level of access is not required the “non-nozzle end”head could be a welded assembly and small hand holes provided forspecific maintenance and bolt down needs.

Referring specifically to FIGS. 19 and 20, a vertical pressure vesselassembly 1221′ includes a top loaded fully welded microchannel reactorassembly with cross flow cooling in its coolant housing. The heatexchange medium 1241 enters via the inlet 1281 and passes into thermalcommunication with the microchannels of the reactor assembly. Thisdesign allows for the entrained hydrogen peroxide bubbles to migrateupward and presumably helps keep the heat exchange surfaces wetted sincethis arrangement inhibits local vapor/liquid separation in the productmanifold. As illustrated, the process catalyst inside the weldedassembly is entombed. Presumably catalyst access would be seldom needed.H₂ and O₂ manifold headers are subassemblies that are welded to theindividual microchannel reactors that include internal distributionmanifolding. After the heat exchange fluid has come into thermalcommunication with the microchannels of the reactor assembly, theresulting fluid is separated into two fluid streams exiting via a heatexchange vapor outlet 1301′ and a heat exchange liquid outlet 1301.

A further detailed exemplary embodiment (not shown) includes a systemthat comprises a microchannel heat exchanger to preheat the reactants, areactor, a microchannel heat exchanger to cool the products, and achilled vapor liquid separator system incorporating the exemplaryembodiments discussed above. The exemplary system is described belowwith appropriate controls to monitor start-up, shut-down, andsteady-state operations of the exemplary embodiments.

The inlet and outlet stream temperatures of an exemplary microchannelreactor is measured using type K thermocouples placed in the connectingtubes to the reactor system approximately 1 to 2 inches from the inletor outlet of the reactor. Pressure transducers are added to each of theinlet and outlet streams at similar locations. Thermocouples are alsoinstalled in thermocouple ports on the outer surface of the reactorsystem along the length of the mixer and reactor sections.

The reactant feed Brooks 5850e series mass flow controllers, NoShokpressure transducers model 1001501127 and 1003001127, Omega latchingrelay controllers model CNI 1653-C24, Swagelok variable pressure reliefvalves, thermal conductivity detector (TCD) gas chromatograph for gasanalysis, etc., were calibrated and verified for proper operation.Flowrates were calibrated against a primary standard calibrator, theDry-Cal DC-2M Primary Flow Calibrator, which was calibrated andcertified by BIOS International. Pressure transducers are calibratedusing a Fluke pressure calibrator model 7181006 with a Fluke 700P07 or700P06 pressure module which were calibrated and certified by Fluke. TheTCD gas chromatograph is calibrated against calibration gases blendedand certified by Praxair Distribution Inc.

The exemplary reactor system was pressure tested by applying a staticpressure approximately 15% higher than the anticipated operatingpressure of the reactor system. If there the leak rate does not exceed0.5 psig in 15 minutes, then the reactor system was considered ready foroperation.

System startup is initiated by flowing nitrogen into the microchannelreactor at a run plan operating pressure at ˜5-8 psig/min in order toheat the microchannel reactor to at 5° C./min to a predeterminedoperating temperature. The outlet condenser system is operated at 4° C.Hydrogen flow is initiated, and as hydrogen is increased the nitrogenflowing through the hydrogen feed line is decreased to maintain constanttotal flow until the nitrogen is off. Then the oxygen flow is slowlyinitiated, and again the nitrogen flowing through the oxygen feed lineis decreased until this nitrogen flow is off. It is to be understoodthat the gaseous reactants, hydrogen and oxygen, are both preheated tothe desired temperature and fed independently to the microchannelreactor. The microchannel reactor performance is monitored bytemperature, pressure and product sampling during operation. Due tosafety considerations, good temperature control is important and thedistributed oxygen feed allows control of the system temperatures asoxygen or hydrogen flow can be increased or decreased to control theoverall temperature and also the location of hottest single pointtemperature in the reactor. Additionally, an inert can be added to thehydrogen or oxygen feed for additional temperature control.

The shutdown procedure is the inverse sequence of the startup, with aninert such as nitrogen being introduced through the oxygen feed line toslowly reduce the oxygen concentration, eventually to approximately zerooxygen concentration. Thereafter, nitrogen is introduced into thehydrogen feed line and the hydrogen flow rate is decreased to reduce thenitrogen concentration, eventually to approximately zero hydrogenconcentration. Once the reactor system is flushed of combustibles andoxidants, the system is cooled and depressurized.

An emergency shutdown system, if activated, would use solenoid valves toshutoff flow of all combustibles and oxidizers, and purge the systemwith nitrogen (or another inert) through both the hydrogen feed line andoxidizer feed line. All power would be shutoff from all heating systems.The emergency shutdown system would be activated by high pressure oneither the oxidizer or hydrogen inlet lines, high temperature on theoxidizer or hydrogen inlet lines, high temperature on the reactor, or byhigh temperature downstream of the reactor. Two pressure relief valveson the main reactor system and a rupture disc on the main vapor-liquidseparator provide additional pressure relief measures. Flame arrestorsin the hydrogen and oxygen feed lines provide an extra measure offlashback protection.

Equal distribution of fluids into all of the reactor microchannels isimportant for efficient operation of the exemplary embodiments. In someexemplary embodiments, it may be advantageous to distribute a reactantinto an adjoining channel where a reaction is taking place. In such aninstance, it may be advantageous to keep the upstream reactant and thecontents of the downstream reaction components separate until the pointof mixing as the distribution of the fluids from macro-scale fluidchannels to the microchannels is designed to achieve the desired flowdistribution.

To achieve these objectives, it is possible for one reactant stream touse a large macro-scale manifold to connect the stream to itsmicrochannels. This implies a direct path between the manifold and theconnecting channels. The direction of the inlet flow in this macro-scalemanifold can be aligned parallel, perpendicular or some angle in-betweenwith regard to the direction of the connecting channels.

One of the reactant streams may use a micro-to-macro (M2M) channel fordistribution within the microchannel unit. An alternate exemplaryembodiment uses a M2M manifold to distribute flow into downstreamchannels that run parallel with the second process channels. Thismanifold is aligned at a nonzero angle to the downstream channels. Analternative to this approach might include using a M2M manifold thatruns parallel with the second process channels and distributes flow todownstream channels that run perpendicular to the second processchannels. Connection channels are made to connect the downstreamchannels to each second process channel. Another option is to usemacro-manifolds to feed distribution channels running perpendicular tothe second process channel. These channels have connection channelsbetween the feed distribution channel for each second process channel.For purposes of the present invention, the quality index factor (Q₁),discussed below, for both the oxidant and hydrogen source are less than30% for a hydrogen peroxide microchannel reactor.

Quality Index Factor “Q₁” is a measure of how effective a manifold is indistributing flow. It is the ratio of the difference between the maximumand minimum rate of connecting channel flow divided by the maximum rate.For systems of connecting channels with constant channel dimensions itis often desired to achieve equal mass flow rate per channel. Theequation for this case is shown below, and is defined as Q₁.

$Q_{1} = {\frac{m_{\max} - m_{\min}}{m_{\max}} \times 100\%}$

wherem_(max) [kg/sec] maximum connecting channel mass flow ratem_(min) [kg/sec]=minimum connecting channel mass flow rate

For cases when there are varying connecting channel dimensions it isoften desired that the residence time, contact time, velocity, or massflux rate have minimal variation from channel to channel such that therequired duty of the unit operation is attained. For those cases wedefine a quality index factor Q₂:

${Q_{2} = {\frac{G_{\max} - G_{\min}}{G_{\max}} \times 100\%}},$

where G is the mass flux rate. For cases when all the connectingchannels have the same cross-sectional area, the equation for Q₂simplifies to Q₁. The quality index factor gives the range of connectingchannel flow rates, with 0% being perfect distribution, 100% showingstagnation (no flow) in at least one channel, and values of over 100%indicating backflow (flow in reverse of the desired flow direction) inat least one channel. In an exemplary form, Q₁ and Q₂ are unadjusted;however, Q₁ and Q₂ may be defined based on the channels that comprise95% of the net flow through the connecting channels. It should be notedthat the lowest flow channels are not counted if the flow through thosechannels is not needed to account for 95% of the net flow through theconnecting channels.

The present invention includes a manifold and at least two connectingchannels that are connected to the header manifold. In the at least twoconnecting channels, differing lengths of the channels have constrictedcross-sectional area. As explained in greater detail below, this designtends to equalize flow through the connecting channels.

A first exemplary chemical processing device comprises: (i) a headermanifold; (ii) at least two parallel connecting channels, a firstconnecting channel and a second connecting channel, connected to theheader manifold, where in each of the at least two parallel connectingchannels, 20% or more of the channel's length is characterized by aconstant cross-sectional area, and 80% or less of the channel's lengthis characterized by a cross-sectional area reduced in size (relative tothe 20% or more of the channel's length that is characterized by aconstant cross-sectional area), and the first connecting channel has alonger length of constant cross-sectional area than does the secondconnecting channel.

The area reduced in size is significantly reduced in size so that flowis restricted; it is not simply a catalyst coating, etc. The reducedarea may also contain a catalyst coating. In some exemplary embodiments,in each of the at least two parallel connecting channels, 50% (or 80%)or more of the channel's length is characterized by a constantcross-sectional area (in some embodiments up to 95% of the length has aconstant cross-sectional area.

A second exemplary chemical processing device (a chemical reactor)comprises at least two parallel connecting channels, a first connectingchannel and a second connecting channel, connected to the headermanifold, where a portion of the first connecting channel and a portionof the second connecting channel contain catalyst, thecatalyst-containing portion of the first connecting channel and thecatalyst-containing portion of the second connecting channel have equaland constant cross-sectional areas, where the first connecting channelhas a first length of reduced cross-sectional area and the secondconnecting channel has a second length of reduced cross-sectional area,and where the first length is less than the second length.

In further exemplary embodiments, the header manifold comprises an inletand the first connecting channel has a shorter length of reducedcross-sectional area than does the second connecting channel; and thefirst connecting channel is closer to the inlet than the secondconnecting channel. Flow passing though the inlet passes into themanifold and momentum tends to force greater flow through the secondconnecting channel; however, the longer constricted flow path in thesecond channel creates greater resistance and tends to equalize flowthrough the connecting channels. In some preferred embodiments themanifold is an L-manifold.

The manifold can be in the plane of the connecting channels or in alayer above or below the plane of the connecting channels.

The edges between areas of a channel (preferably a microchannel) thatare reduced in cross-sectional area can be sloped (such as by etching)or stepwise (such as by bonded, stamped shims). The areas of a channelthat are reduced in cross-sectional area can be disposed at thebeginning of channel (next to the header manifold), the end of channel,or in the middle of the channel. The areas of a channel that are reducedin cross-sectional area can be continuous or dispersed along a channel'slength.

The present invention also includes exemplary methods of fabricatingchemical processing devices (e.g., a chemical reactor), where the methodcomprises: (i) stacking plural laminae into a stack of laminae, where atleast one of the plural laminae comprises at least two parallelconnecting channels, a first connecting channel and a second connectingchannel, where in each of the at least two parallel connecting channels,20% or more of the channel's length is characterized by a constantcross-sectional area, and 80% or less of the channel's length ischaracterized by a cross-sectional area reduced in size (relative to the20% or more of the channel's length is characterized by a constantcross-sectional area), and where the first connecting channel has alonger length of constant cross-sectional area than does the secondconnecting channel and the at least two parallel connecting channels areconnected to a header manifold.

In further exemplary embodiments, the connecting channels are partiallyetched into a shim—channels of the desired structure could also bemolded, formed by a deposition process, or combinations of these.Preferably, slots are formed through the entire thickness of a layer.Similarly, the invention includes methods of making laminated chemicalreactors in which catalyst is deposited in the constant area portions.

The present invention also includes prebonded assemblies and laminateddevices of the described structure and/or formed by the methodsdescribed herein. Laminated devices can be distinguished fromnonlaminated devices by optical and electron microscopy or other knowntechniques. The invention also includes methods of conducting chemicalprocesses in the devices comprising flowing a fluid through a manifoldand conducting a unit operation in the connecting channels.

In further exemplary embodiment, channel heights may be altered orreduced for varying lengths to control the pressure drop and thus flowdistribution to many parallel microchannels. In such an embodiment, theprocess flow microchannel is comprised of at least two or more shims orlamina that are stacked on top of each other. Each shim contains throughslots and are stacked between two wall shims to form a hermeticallysealed microchannel after bonding.

For example, when two lamina with through slots stacked to form themicrochannel height, the first lamina may have a shorter slot than theat least second lamina. The resulting microchannel would have a firstheight for a first distance along the length of the microchannel beforeopening to the second height which represents the combined height of theat least two slots stacked on top of each other. It should be noted thatthe final channel height after diffusion bonding may be slightly smaller(e.g., up to 10% smaller) as a result of the compressive nature of thediffusion bonding process.

In some further exemplary embodiments, in a second channel, the firstheight (reduced cross-sectional area) as represented by the shimthickness of the first lamina would have second length that is longerthan the first length in the first channel. The resulting pressure dropin the second channel would be larger than the pressure drop in thefirst channel. A third channel and so on could have a third length ofthe first height that is preferably longer than the second length.

In some additional exemplary embodiments, the lengths of reducedcross-sectional area may be utilized anywhere in the channels, or inmultiple places in the channels, not just near or adjacent to themanifold. Possible locations for these flow distribution featuresinclude adjacent to the inlet manifold, adjacent to the outlet manifold,or anywhere in the channels which connect to the manifold(s) orsub-manifolds, in any sub-manifold sections, when present, or anycombination of the preceding locations. This offers a distinct advantageover conventional manifold designs, in that these features can be placedin strategic locations where they can serve more than one purpose, suchas adding stability by connecting long ribs between continuous channels,providing enhanced mixing, providing more uniform flow distribution overa wider range of flow rates, and providing less sensitivity to tolerancein the channel dimensions. Flow distribution features may also beincluded in multiple locations in each channel to better provide a moreuniform pressure at points in channels where interconnectedness ispresent, thereby minimizing flow redistribution among channels at thosepoints.

Another potential advantage of the present invention over conventionalflow distribution techniques is more robust performance over a widerrange of flow rates. For instance, in one embodiment for which the flowdistribution features in each channel differ only in length (rather thancross section), the contraction and expansion losses in each channel aresimilar, and the resistance to flow scales more linearly with flow ratein each channel than for other types of flow distribution features whichrely on different magnitudes of contraction and expansion losses (flowresistance) in each channel. In cases where the majority of flowresistance in each flow path scales more or less linearly, such flowdistribution features will give a more robust flow distribution (moreuniform) over a wider range of flow conditions.

In certain exemplary embodiments, there may be two, three, five, ten, ormore different first lengths of the first height of parallelmicrochannels.

The microchannels may be made of two or three or more lamina with slotsstacked on top of each other. The microchannels may have a first height,a second height, and a third height or more. There may also be acorresponding first length, second length, and third length or more. Inan alternate embodiment, a first length having a first height may beadjacent to a second length having a second height. The second lengthcan be adjacent to a third length having a third height, etc.

This method of tailoring the pressure drop in each microchannel toimprove the flow distribution is especially useful for a method ofmanufacturing that relies on stacking stamped lamina. It is furtherpreferable to use a nibbling approach to stamping such that minimaladditional stamping dies are required to form the first and second ormore lengths of microchannels that maintain the first height. The laminais preferentially held on a table that has controls to move in both thex and y directions. The shim or lamina is moved such that the die strokecuts the desired length of through slot in each lamina. In the nibblingprocess die strokes cut a fraction of the total slot length and thenmove to cut an adjacent slot. The adjacent slot may be connected ornearby the first slot. The die stamp that is 2 inches, as an example,can cut a full slot of 2 inches in a single stroke, or can cut a shorterslot of 1.99″ or 1.9″ or 1.5″ or 1″ or any dimension in a single strokewithin the tolerance of the x-y table controls for moving the lamina.Overall the die can cut a larger slot, but the lamina must move for thedie to create a larger slot. The length of the die stamp does notchange, but rather the lamina moves such that the die stamps over apreviously cut or stamped region while simultaneously cutting a freshsection of metal less than the full die length. By this manner, minimaladditional fabrication complexity is added to form a first channel witha first height and a first length adjacent to a second channel with afirst height and a preferential second length for purposes ofcontrolling flow distribution. See FIG. 28.

In an alternate exemplary embodiment, two lamina may be stacked on topof each other to form a microchannel, where one or both lamina arepartially etched to create an analogous first length and first heightthat is different from the second length and second height. One laminamay be partially etched, while the second or third or more lamina havethrough slots that are all stacked to form the microchannel.

In a further alternate embodiment, flow restrictions may be placedwithin the micromanifold region rather than or in addition to themicrochannels. The method of stacking lamina with through slots oropenings is especially helpful for this approach. A first length of thefirst height in the first submanifold may be longer than the secondlength of the first height of the second submanifold. By this manner,pressure drop in one submanifold may be made more uniform between thefirst and second submanifold to improve the flow distribution betweenthe at least first and second submanifold.

This method of flow distribution within microchannels may also bepreferential for cross flow microchannels that may not have amicromanifold region as required to distribute the flow laterally acrossthe device within the device. In cross-flow devices it may bepreferential to join a large open or macromanifold opening to the faceof the open set of parallel microchannels. In this case, flowdistribution may be enabled by creating a first length of a first heightin a first microchannel that is different from a first height of asecond length in the at least second microchannel. The first and secondlength may be made by stacking stamped lamina, or it may be made bypartially removing material from a single lamina such that a continuousfirst microchannel has a first height for a first length and a secondheight for a third length along the microchannel length and a continuoussecond microchannel has a first height for a second length and a secondheight for a fourth length. In an alternate embodiment, the lamina maycontain at least a first microchannel with a first height for a firstlength and a second height for a third length. In addition the laminamay contain at least a second microchannel with a third height for afifth length and a fourth height for a six length. Any combination ofheights and lengths of sections along a continuous microchannel may bepossible.

In further exemplary embodiments, the width of each microchannel issubstantially constant along its length and each channel in a set ofconnecting channels have substantially constant widths; “substantiallyconstant” meaning that flow is essentially unaffected by any variationsin width. For these examples the width of the microchannel is maintainedas substantially constant. Where substantially constant is definedwithin the tolerances of the fabrication steps. It is preferred tomaintain the width of the microchannel constant because this width is animportant parameter in the mechanical design of a device in that thecombination of microchannel width with associated support ribs on eitherside of the microchannel width and the thickness of the materialseparating adjacent lamina or microchannels that may be operating atdifferent temperatures and pressures, and finally the selected materialand corresponding material strength define the mechanical integrity orallowable temperature and operating pressure of a device. If the widthwere allowed to vary across a lamina, such as in the Golbig reference,then the material thickness between adjacent lamina would have to besized based on the widest microchannel. As such, additional materialwould be required for this design. In addition, varying microchannelwidths would require multiple tooling for stamping and increase thecomplexity of fabrication.

Features like protrusions can be added to the parallel connectingchannels to serve a dual purpose. The size of the features can be usedto regulate the channel to channel pressure drop variation whichprovides control on distributing flow among the connecting channels.Besides, the features provide improvement in the heat transfercharacteristic of the channel. The features could be protrusions fromthe wall with any shape like round, square, pyramidal etc. Some of theshapes of the features are shown in FIG. 21. These features can belocated only at a portion of the connecting channels.

Example cross sections of microchannels with varying channel gaps andsection lengths is shown in FIG. 29. The smaller microchannel gaps maybe found near the front, end, middle, or anywhere within themicrochannel. For the case of three or more slot lamina stacked to forma microchannel between two wall plates, the restriction may be placed inthe center lamina or lamina not adjacent to the wall shim.

The present invention was used in conjunction with a flow distributionmodel to dramatically improve the predicted flow distribution uniformityfor 25 SLPM of air at 25° C. and 1.01 bar outlet pressure among tenchannels connected to a common inlet manifold. For this example thedimensions of each channel were 1.02 mm by 4.06 mm wide extending 25.4cm long. Each channel was separated by a 1.52 mm wide wall (for a totalof 5.59 mm from leading edge to leading edge of adjacent channels). Thecommon manifold was 1.02 mm gap by 10.16 mm width and 54.4 mm in lengthis defined in the direction of the inlet flow stream and orthogonal tothe direction of flow in the parallel microchannels, as shown in FIG. 22as a negative model. The model gave a predicted flow distributionquality factor of >89% for the geometry described above without the useof the present invention. The model results for this baseline case areshown in FIG. 23. The predicted pressure drop for the baseline case was5027 Pa.

A second case was run with the same geometry except that flowdistribution features which reduced the channel gap from 1.02 mm to 0.25mm were added in the portion of each channel which is connected to themanifold. These features created channel dimensions of 0.25 mm by 4.06mm wide, with varying lengths designed to minimize the quality factor(that is, maximize the degree of flow distribution uniformity). Thetotal length of each channel, including the flow distribution featureswas maintained constant at 25.4 cm. With the flow distribution featuresincluded, a quality factor of <0.4% was predicted. The flow distributionfeature lengths for each channel are shown in Table yy, and theresulting flow distribution is depicted in FIG. 25. The predictedpressure drop for the case including the inventive features was 5517 Pa(490 Pa higher than the baseline case without the features.) In FIG. 24,the channels with the longest length features have the most flowresistance in the microchannel. These values were obtained byiteratively changing the flow distribution feature length at eachsuccessive iteration by a factor proportional to the mass flow throughthe channel predicted for the previous iteration. These factors may benormalized such that their average value is 1. Although an infinitenumber of solutions may exist which provide adequate flow distributionuniformity, shorter lengths tend to minimize pressure drop, and theshortest length should not be less than is practical for manufacturingpurposes.

Referencing FIG. 21, any given process will have a number of differentcontrolled variables. For each such variable, an associated manipulatedvariable must be chosen and be tied to it via the appropriate feedbackcontrol hardware.

There are non-dynamic and dynamic individual components in a feedbackcontrol loop. The non-dynamic components have no time-dependentbehavior, i.e. no lag in their operation. From a mathematical sense, itis algebraic in nature. In fact, it is often referred to as gain of thecomponent. These kinds of components cannot predicatively be handledwith a dynamic process, such as a hydrogen peroxide reactor, whereoscillation or fluctuation of the output variables needs to be adjustedto a set point. The frequently encountered condition is that the outputof the component has a lag to the input, such as in a process itself.Thus, “dynamic” control components are most often utilized in a processcontrol loop. The specific mathematical form of these dynamic lags is adifferential equation with time as the independent variable.

Generally, to control a dynamic process, using only non-dynamic(proportional) and differential components often results in an errorsignal in control input, causing, for example, “overshot”. This problemmay become severe when the deviation in the output variable is of asmall amplitude but not a small frequency such as a fluctuation. Thus,reset action in the control loop may be used. The value of themanipulated variable is changed at a rate proportional to the error. Thereset action is also called “integral action”. The core of moderncontrol concept is called “PID” (Proportional+Integral+Derivative) thatis the most suited for a process control of fluctuation in a smallamplitude and is expressed as K(1+1/T_(i)P+T_(d)P).

Referencing FIG. 22, gain is a proportional factor between the errorinput signal and the output of a control component. The gain K iscalculated as K=output/input. The gain of the controller is alsoreferred to as the proportional sensitivity of the controller. Itindicates the change in the signal to the manipulated variable per unitchange in the error signal. In a very true sense, the proportionalsensitivity or gain is an amplification and represents a parameter on apiece of actual hardware which must be adjusted by the operator, i.e.,the gain is a knob to adjust (or a number to change in a computer).

The gain-adjusting mechanism on many industrial controllers is oftenexpressed in terms of proportional band (PB). PB is defined as the spanof values of the input that corresponds to a full change in the output:

${PB} = {\frac{1}{K} \times 100}$

In an exemplary application as a control valve, PB is often inferred tothrough a full stroke.

Time constant of a system is a measure of output response in time orfrequency domain with respect to a disturbance (including change ininput) to the system in steady state. In physical terms, it representscapacitance divided by conductance. It is system-dependent and, thus,its definition depends on the characteristics of the system. For a firstorder system, it is defined in frequency domain as

${\frac{U_{o}(s)}{U_{c}(s)} = {K\; \frac{1}{1 + {\tau \; s}}}},$

where U_(o) is the output after the disturbance, U_(c) is the output atits original steady state, K is gain and s is the frequency variable. Intime domain (before Laplace transformation), it is written as

${{\tau \; \frac{U_{o}}{t}} + U_{o}} = {U_{c}.}$

After integration, the output is described as

U _(o) −U _(f)=(U _(c) −U _(f))(1−e ^(−t/τ)),

where U_(f) is the reference value of the output and it can be theoutput when the new steady state is established. At time t=τ, thedifference U_(o)−U_(f) reaches 63.3% of the total output changeU_(c)−U_(f). It is recognized that the time constant for a microchannelreactor is considerably shorter than a conventional reactor as denotedby the relatively short residence times for chemical conversion. Assuch, the output after a disturbance (U_(o)) will reach the new outputvalue in a time proportional to the system gain (K) multiplied by theoriginal steady-state output (U_(c)), or a net shorter time over asystem with a longer time constant. From this, the changes may be madeto the process control scheme more quickly to get the process back tothe desired output. The net reduction in time for off-specificationperformance increases the overall productivity of the microchannelreactor.

As discussed previously, the exemplary embodiments of the presentinvention are adapted to accommodate high production rates of thedesired product, as the configurations are additive and may bemultiplied to achieve greater outputs. Closely placed walls of themicrochannels help maintain laminar flow that further stabilizes thedispersion. The placement and orientation of the walls also gives riseto better holdup distribution profiles across the flow channels andregulation of multi-phase flow such that the coalescence of bubbles (gasdispersion in liquid) or droplets (liquid dispersion in another liquid)occurs less frequently. The construction techniques of the microchannelsmay also function as a continuous heat flow network to either supply ordisperse reaction heat, with continuous dispersion along the flow pathautomatically controlled.

In a still further exemplary embodiment, the reactive or non reactivefluid streams exchange heat with a heat exchange fluid flowing through aheat exchange channel, which in exemplary form includes a microchannel,having a rectangular cross section and being adjacent to the processmicrochannel or the liquid channel. During operation of the microchannelprocess units (exemplary embodiments), the microchannels carrying thereactants and products may be heated or cooled using heat exchangechannels, which in exemplary form are microchannels. The heat exchangechannels are adapted for heat exchange fluid to flow through thechannels in a direction parallel to and co-current with the flows ofmaterial through the process microchannels. Alternatively, the heatexchange fluid may flow through the heat exchange channels in adirection opposite to the direction of reactants or products, and thusflow countercurrent to the flow of material through the processmicrochannels. Still further, the heat exchange channels may be orientedrelative to the process microchannels to provide for the flow of heatexchange fluid in a direction that is cross-current relative to the flowthrough the process microchannels. The heat exchange channels may alsohave a serpentine configuration to provide a combination of cross-flow,co-current, and/or counter-current flow.

Exemplary internal dimensions for the heat exchange channels include aheight or width of up to about 10 mm, and in a more detailed exemplaryembodiment about 0.05 to about 10 mm. A second exemplary internaldimension encompasses various values such as, for example, from about 1mm to about 1 m. The length of the heat exchange channels also encompassvarious values such as, for example, from about 1 mm to about 1 m. Theseparation between each process microchannel and the next adjacent heatexchange channel associated with wall thickness encompass exemplaryranges from about 0.05 mm to about 5 mm.

The heat exchange fluid may be any fluid capable of heat transfer. Suchfluids include, without limitation, air, steam, liquid water, gaseousnitrogen, liquid nitrogen, other gases including inert gases, carbonmonoxide, molten salt, oils such as mineral oil, and heat exchangefluids such as Dowtherm A and Therminol that are commercially availablefrom Dow-Union Carbide. The heat exchange fluid may also comprise thefirst fluid and/or second fluid. This can provide process pre-heat orpre-cooling and increase overall thermal efficiency of the process.

It is also within the scope of the invention that the heat exchangechannels comprise process channels where an endothermic process isconducted therein. These heat exchange process channels may includemicrochannels. Examples of endothermic processes that may be conductedin the heat exchange channels include steam reforming anddehydrogenation reactions. In an exemplary embodiment, the incorporationof a simultaneous endothermic reaction to provide an improved heat sinkmay enable a typical heat flux of roughly an order of magnitude or moreabove the convective cooling heat flux.

It is further within the scope of the invention that the heat exchangefluid undergoes a phase change as it flows through the heat exchangechannels. This phase change provides additional heat removal from theprocess microchannels beyond that provided by convective cooling. For aliquid heat exchange fluid being vaporized, the additional heat beingtransferred from the process microchannels would result from the latentheat of vaporization. An example of such a phase change would be an oilor water that undergoes partial or complete boiling. In a more detailedexemplary embodiment, the percent boiling of the phase change fluid maybe up to or over 50%.

The heat flux for convective heat exchange or convective cooling in themicrochannel heat exchanger includes ranges from about 1 to about 25watts per square centimeter of surface area of the process microchannels(W/cm²) in the microchannel heat exchanger. The heat flux for phasechange heat exchange includes ranges from about 1 to about 250 W/cm².The heat exchange channels, which may be adjacent to the processmicrochannels may provide a relatively short heat transport anddiffusion distance which provides for the ability to heat and cool thereactants or products rapidly with decreased temperature gradients. As aresult, products that may not necessarily be suitable for prolongedheating or would degrade under large temperature gradients may beprepared using the inventive process of the present invention.

The microchannel reactors of the present invention may be constructed ofany material that provides sufficient strength, dimensional stabilityand heat transfer characteristics for carrying out the inventiveprocess. Examples of suitable materials include steel (e.g., stainlesssteel, carbon steel, and the like), aluminum, titanium, nickel, andalloys of any of the foregoing metals, plastics (e.g., epoxy resins, UVcured resins, thermosetting resins, and the like), monel, inconel,ceramics, glass, composites, quartz, silicon, or a combination of two ormore thereof. The microchannel reactor may be fabricated using knowntechniques including wire electrodischarge machining, conventionalmachining, laser cutting, photochemical machining, electrochemicalmachining, molding, water jet, stamping, etching (for example, chemical,photochemical or plasma etching) and combinations thereof. Themicrochannel reactor may be constructed by forming layers or sheets withportions removed that allow flow passage. A stack of sheets may beassembled via diffusion bonding, laser welding, diffusion brazing, andsimilar methods to form an integrated device. Stacks of sheets may begasketed together to form an integral device. The microchannel reactorhas appropriate manifolds, valves, conduit lines, etc. to control flowof the reactant composition and product, and flow of the heat exchangefluid. These are not shown in the drawings, but can be readily providedby those skilled in the art.

The process feed stream entering the process microchannels may compriseO₂, H₂, or a mixture thereof. The concentration of O₂ may range fromabout 1 to about 99% by volume, and in one embodiment about 20 to about70% by volume. The concentration of H₂ may range from about 1 to about99% by volume, and in one embodiment about 20 to about 70% by volume.The process feed stream may further comprise water, methane, carbonmonoxide, carbon dioxide or nitrogen.

The staged addition feed stream entering the staged additionmicrochannels may comprise O₂ or H₂. The concentration of O₂ or H₂ mayrange from about 1 to about 100% by volume, and in one embodiment about50 to about 100% by volume. The staged addition feed stream may furthercomprise water, methane, carbon dioxide, carbon monoxide or nitrogen.

The total molar ratio of H₂ to O₂ in the process feed stream and stagedaddition feed stream entering the process microchannels may range fromabout 0.1 to about 10, and in one embodiment about 0.5 to about 2.

The H₂ in the process feed stream and/or the staged addition feed streammay be derived from another process such as a steam reforming process(product stream with H₂/CO mole ratio of about 3), a partial oxidationprocess (product stream with H₂/CO mole ration of about 2), anautothermal reforming process (product stream with H₂/CO mole ratio ofabout 2.5), a CO₂ reforming process (product stream with H₂/CO moleratio of about 1), a coal gasification process (product stream withH₂/CO mole ratio of about 1), and combinations thereof. With each ofthese feed streams the H₂ may be separated from the remainingingredients using conventional techniques such as membranes oradsorption.

The O₂ in the process feed stream and/or the staged addition feed streammay be pure oxygen or it may be derived from air or nitrous oxides. TheO₂ may be separated using conventional techniques such as cryogenicdistillation, membranes, and adsorption. The presence of contaminantssuch as sulfur, nitrogen, halogen, selenium, phosphorus, arsenic, andthe like, in the process feed stream and/or the staged addition feedstream may be undesirable. Thus, in one embodiment of the invention, theforegoing contaminants may be removed from the process feed streamand/or the staged addition feed stream or have their concentrationsreduced prior to conducting the inventive process. Techniques forremoving these contaminants are well known to those of skill in the art.For example, ZnO guardbeds may be used for removing sulfur impurities.In one embodiment, the contaminant level in the process feed streamand/or the staged addition feed stream may be at a level of up to about10% by volume, and in one embodiment up to about 5% by volume, and inone embodiment up to about 2% by volume, and in one embodiment up toabout 1% by volume, and in one embodiment up to about 0.1% by volume,and in one embodiment up to about 0.01% by volume.

The heat exchange fluid may be any fluid. These include air, steam,liquid water, gaseous nitrogen, liquid nitrogen, other gases includinginert gases, carbon monoxide, molten salt, oils such as mineral oil, andheat exchange fluids such as Dowtherm A and Therminol which areavailable from Dow-Union Carbide.

The heat exchange fluid may comprise a stream of the reactantcomposition. This can provide process pre-heat and increase in overallthermal efficiency of the process. In one embodiment, the heat exchangechannels comprise process channels wherein an endothermic process isconducted. These heat exchange process channels may be microchannels.Examples of endothermic processes that may be conducted in the heatexchange channels include steam reforming and dehydrogenation reactions.In one embodiment, the incorporation of a simultaneous endothermicreaction to provide an improved heat sink may enable a typical heat fluxof roughly an order of magnitude or more above the convective coolingheat flux. The use of simultaneous exothermic and endothermic reactionsto exchange heat in a microchannel reactor is disclosed in U.S. patentapplication Ser. No. 10/222,196, filed Aug. 15, 2002, which isincorporated herein by reference.

The cooling of the process microchannels during the inventive process,in one embodiment, is advantageous for reducing the possibility ofexplosions and/or detonations due to the use of O₂ and H₂. As a resultof this cooling, in one embodiment, the temperature of the process feedstream at the entrance to the process microchannels may be within about200_C, and in one embodiment within about 100_C, and in one embodimentwithin about 50_C, and in one embodiment within about 20_C, of thetemperature of the product exiting the process microchannels.

The exemplary embodiments of the present invention may utilizemicrochannels that may be operated in a flammable regime with channelgaps that not only exceed the quench gap, but even exceed criticaldetonation gap sizes, but still provide safe operation. The possibilityof detonation can be eliminated by several methods, that include withoutlimitation: (a) limit the channel gap to a critical value known as thedetonation cell size, λ; (b) allow the channel gap to exceed λ but limitthe channel length to a critical value known as the detonation run-uplength, L*; and, (c) ensure the combustion flame speed remains in thelaminar regime. Each of these methods is discussed in order below.

A microchannel process is inherently safe when the channel gap is belowthe safe quenching distance, which is the maximum allowable distancethat ensures suppression of all flame propagation at a specific pressureand temperature condition. As the channel gap increases, flamepropagation may be possible within the flammable limits. For asufficiently large channel gap and under the necessary composition andthermodynamic conditions, a flame may become a deflagration, defined asa combustion wave propagating at subsonic velocity relative to theunburned gas immediately ahead of the flame with flame speeds in therange of 1 m/s to 1000 m/s. Empirical studies using detonation ofhydrogen in air indicate the minimum gap for high aspect ratio channelsto support detonation transmission is at least as large as thecomposition detonation cell size, λ, a quantity that is approximately anorder of magnitude greater than the quenching distance. This guidanceholds for channels of all aspect ratio.

When the channel gap exceeds an experimentally measured quantity calledthe detonation cell size, for rectangular channels or any aspect ratio,a flame propagating through a premixed fuel/oxidant stream mayaccelerate through a sufficiently long length of channel to transitionto a detonation. A detonation is defined as a combustion wavepropagating at supersonic speed relative to the unburned gas immediatelyahead of the flame. Unlike a deflagration wave, which is associated witha relatively weak overpressure field of at most one atmosphere, adetonation wave can generate a much more intense blast field withoverpressure in the range of 1 to 20 atmospheres.

In order for the transition from deflagration to detonation to takeplace, the flame propagation speed must accelerate to flame speeds ofnearly 2000 m/s for most hydrocarbon/air mixtures. Detonation velocitiesfor some typical fuel species in stoichiometric proportions with air atatmospheric pressure are at least one order of magnitude greater thantypical flow velocities in micro-channel applications. Furthermore,there is a chemical induction period, which is usually related tochannel length that must be available for acceleration up to thecritical velocity. This transition length is typically on the order ofseveral meters—much longer than typical microchannel applications.Finally, the feedback mechanism for a detonation generally relies onturbulent flow at the propagating flame front.

Referencing FIG. 23, flame acceleration and turbulence levels areenhanced by certain classes of obstacles to flow in the flow streampath. These classes of obstacles would include periodic or non-periodicplacement of bluff restrictions to flow such as channel support ribsoriented cross-stream to the bulk flow direction.

Referencing FIG. 24, there are engineered features in microchannels thatcan actually serve to suppress turbulence or stretch the flame in such amanner that a detonation wave cannot be supported. Examples of thesetype of configurations would include fin structures oriented in thedirection of flow.

In sum, if all of these conditions are not met, namely (1) channel gapsexceeding a critical size, (2) channel lengths permitting flameacceleration up to a critical detonation velocity, and (3) turbulentflame propagation, then detonation cannot take place. Therefore,microchannels may be safely applied in flammable regimes not acceptablein typical macro-scale applications.

The catalyst for use with the present invention may comprise anycatalyst suitable for the direct production of hydrogen peroxide from O₂and H₂. The catalyst may comprise at least one catalytically activemetal or oxide thereof. The catalyst may comprise a metal from GroupVIII of the Periodic Table, or an oxide thereof, or a mixture of two ormore thereof. The catalyst may comprise Co, Fe, Ni, Ru, Rh, Pd, Ir, Pt,Os, or an oxide thereof, or a combination of two or more thereof. In oneembodiment, the catalyst further comprises a catalyst support. Thesupport material may comprise a ceramic, alumina, zirconia, silica,aluminum fluoride, bentonite, ceria, zinc oxide, silica-alumina, siliconcarbide, a refractory oxide, molecular sieves, diatomaceous earth, or acombination of two or more thereof. Examples of catalysts that may beused include those disclosed in U.S. Pat. Nos. 3,336,112; 4,009,252;4,389,390; 4,681,751; 4,772,458; 4,832,938; 4,889,705; 5,104,635;5,135,731; and 6,576,214 B2; these patents being incorporated herein byreference for their disclosures of catalysts suitable for the productionof hydrogen peroxide from oxygen and hydrogen, and methods for preparingsuch catalysts.

The catalyst used in a microchannel reactor may have any size andgeometric configuration that fits within the process microchannels. Thecatalyst may be in the form of particulate solids (e.g., pellets,powder, fibers, and the like) having a median particle diameter of about1 to about 1000 μm, and in one embodiment about 10 to about 500 μm, andin one embodiment about 25 to about 250 μm. In one embodiment, thecatalyst is in the form of a fixed bed of particulate solids.

In an exemplary embodiment, the catalyst is in the form of a fixed bedof particulate solids, the median particle diameter of the catalystparticulate solids is relatively small, and the length of each processmicrochannel is relatively short. The median particle diameter may be inthe range of about 1 to about 1000 □m, and in one embodiment about 1 toabout 500 □m, and the length of each process microchannel may be in therange of up to about 10 meters, and in one embodiment about 1 cm toabout 10 meters, and in one embodiment about 1 cm to about 5 meters, andin one embodiment about 1 cm to about 2 meters, and in one embodimentabout 1 cm to about 1 meter, and in one embodiment about 1 to about 25cm.

The catalyst may be supported on a porous support structure such as afoam, felt, wad or a combination thereof. The term “foam” is used hereinto refer to a structure with continuous walls defining pores throughoutthe structure. The term “felt” is used herein to refer to a structure offibers with interstitial spaces therebetween. The term “wad” is usedherein to refer to a support having a structure of tangled strands, likesteel wool. The catalyst may be supported on a support having ahoneycomb structure or a serpentine configuration. The catalyst can beloaded on portions of the flow-by catalyst support structure. An exampleof this is to load the catalyst only in the section close to theinterface of the support structure and the flow-by stream. Near theinterface the reactant concentrations are at the higher level, the dropsignificantly into the depth of the support structure.

The catalyst may be supported on a flow-by support structure such as afelt with an adjacent gap, a foam with an adjacent gap, a fin structurewith gaps, a washcoat on any inserted substrate, or a gauze that isparallel to the flow direction with a corresponding gap for flow. Anexample of a flow-by structure is illustrated in FIG. 25. In FIG. 25 thecatalyst 800 is contained within process microchannel 802. An openpassage way 804 permits the flow of the reactants through the processmicrochannel 802 in contact with the catalyst 800 as indicated by arrows806 and 808.

The catalyst may be supported on a flow-through support structure suchas a foam, wad, pellet, powder, or gauze. An example of a flow-throughstructure is illustrated in FIG. 26. In FIG. 26, the flow-throughcatalyst 810 is contained within process microchannel 812 and thereactants flow through the catalyst 810 as indicated by arrows 814 and816.

The support may be formed from a material comprising silica gel, foamedcopper, sintered stainless steel fiber, steel wool, alumina, poly(methylmethacrylate), polysulfonate, poly(tetrafluoroethylene), iron, nickelsponge, nylon, polyvinylidene difluoride, polypropylene, polyethylene,polyethylene ethylketone, polyvinyl alcohol, polyvinyl acetate,polyacrylate, polymethylmethacrylate, polystyrene, polyphenylenesulfide, polysulfone, polybutylene, or a combination of two or morethereof. In one embodiment, the support structure may be made of a heatconducting material, such as a metal, to enhance the transfer of heataway from the catalyst.

The catalyst may be directly washcoated on the interior walls of theprocess microchannels, grown on the walls from solution, or coated insitu on a fin structure. The catalyst may be in the form of a singlepiece of porous contiguous material, or many pieces in physical contact.In one embodiment, the catalyst may be comprised of a contiguousmaterial and has a contiguous porosity such that molecules can diffusethrough the catalyst. In this embodiment, the fluids flow through thecatalyst rather than around it. In one embodiment, the cross□sectionalarea of the catalyst occupies about 1 to about 99%, and in oneembodiment about 10 to about 95% of the cross□sectional area of theprocess microchannels. The catalyst may have a surface area, as measuredby BET, of greater than about 0.5 m2/g, and in one embodiment greaterthan about 2 m2/g, and in one embodiment greater than about 5 m2/g, andin one embodiment greater than about 10 m2/g, and in one embodimentgreater than about 25 m2/g, and in one embodiment greater than about 50m2/g.

In microchannel processes, washcoating sufficient catalyst onto flatprocess channel walls may become a challenge. The layer thickness of thecoating solution left on the flat walls after a coating and drainingpass is generally thin and the dried layer doesn't contain desiredloading. The thin layer in microchannels is a resultant of low viscosityand low surface tension fluid needed to drain and avoid blocking themicrochannel and other structures in fluid communication therewith, suchas, without limitation, oxidant jet holes. For example, for an aqueous15% Alumina SOL solution at a viscosity of 2.6 cP, density 1100 kg/m3,and surface tension 0.068 N/m, the layer directly after draining is only25-50 μm in a vertical channel having a gap of 0.04 inches, as is shownin FIG. 27 from a computational fluid dynamics (CFD) simulation assuminga zero contact angle.

Microfin or grooves structures may increase the liquid hold-up of thewall and, in turn, the catalyst loading. The larger the structure is insize, the more liquid that can be held therein as long as the size issmaller than the capillary force acting range (determined by Laplacelength). Another factor that determines the liquid hold-up is thecontact angle of the liquid on the surface, as is illustrated in FIG.28.

Obviously, a liquid with a larger contact angle is desired. However, dueto fabrication limits, only one side of the channel includes a microfinin the microchannel, while the other side is a flat wall. A liquid witha large contact angle poorly wets the flat surface, as such a liquidwith a small contact angle is needed at least for wetting the flat wall.In addition, the microfin may also become filled via wetting.

The washcoating process includes two exemplary formulations. One isoptimized with a small contact angle for a flat surface and microfininitial wetting, while the other is optimized with a large contact anglefor microfins' large liquid hold-up. The different formulations areseparately filled into and drained from the microchannel so that amaximum catalyst loading of the channel can be achieved. Smaller contactangles may be achieved by adding surfactant into the coating solutionor/and treating the wall surface (make it rough or reduce the surfaceenergy in certain ways) as well as choosing certain solvents (fi.hydrocarbon) as the solution. Larger contact angles can be achieved, forexample, by choosing organic compositions of liquid and wall materialand/or treating the surface (coating, polishing, etc). The polarity ofthe wall surface and liquid can also be tailored to match thecompatibility of the liquid/wall for a large liquid hold-up.

The catalyst may comprise a porous support, an interfacial layeroverlying the porous support, and a catalyst material dispersed ordeposited on the interfacial layer. The interfacial layer may besolution deposited on the support or it may be deposited by chemicalvapor deposition or physical vapor deposition. In one embodiment thecatalyst comprises a porous support, optionally a buffer layer overlyingthe support, an interfacial layer overlying the support or the optionalbuffer layer, and a catalyst material dispersed or deposited on theinterfacial layer. Any of the foregoing layers may be continuous ordiscontinuous as in the form of spots or dots, or in the form of a layerwith gaps or holes.

The porous support may have a porosity of at least about 5% as measuredby mercury porosimetry and an average pore size (sum of pore diametersdivided by number of pores) of about 1 to about 1000 μm. The poroussupport may be made of any of the above indicated materials identifiedas being useful in making a support structure. The porous support maycomprise a porous ceramic support or a metal foam. Other porous supportsthat may be used include carbides, nitrides, and composite materials.The porous support may have a porosity of about 30% to about 99%, and inone embodiment about 60% to about 98%. The porous support may be in theform of a foam, felt, wad, or a combination thereof. The open cells ofthe metal foam may range from about 20 pores per inch (ppi) to about3000 ppi, and in one embodiment about 20 to about 1000 ppi, and in oneembodiment about 40 to about 120 ppi. The term “ppi” refers to thelargest number of pores per inch (in isotropic materials the directionof the measurement is irrelevant; however, in anisotropic materials, themeasurement is done in the direction that maximizes pore number).

The buffer layer, when present, may have a different composition and/ordensity than both the porous support and the interfacial layers, and inone embodiment has a coefficient of thermal expansion that isintermediate the thermal expansion coefficients of the porous supportand the interfacial layer. The buffer layer may be a metal oxide ormetal carbide. The buffer layer may be comprised of Al2O3, TiO₂, SiO₂,ZrO₂, or combination thereof. The Al2O3 may be αAI2O3, γAI2O3 or acombination thereof. αAI2O3 provides the advantage of excellentresistance to oxygen diffusion. The buffer layer may be formed of two ormore compositionally different sublayers. For example, when the poroussupport is metal, for example a stainless steel foam, a buffer layerformed of two compositionally different sublayers may be used. The firstsublayer (in contact with the porous support) may be TiO₂. The secondsublayer may be α□AI2O3 which is placed upon the TiO₂. In oneembodiment, the α□AI2O3 sublayer is a dense layer that providesprotection of the underlying metal surface. A less dense, high surfacearea interfacial layer such as alumina may then be deposited as supportfor a catalytically active layer.

The porous support may have a thermal coefficient of expansion differentfrom that of the interfacial layer. In such a case a buffer layer may beneeded to transition between the two coefficients of thermal expansion.The thermal expansion coefficient of the buffer layer can be tailored bycontrolling its composition to obtain an expansion coefficient that iscompatible with the expansion coefficients of the porous support andinterfacial layers. The buffer layer should be free of openings and pinholes to provide superior protection of the underlying support. Thebuffer layer may be nonporous. The buffer layer may have a thicknessthat is less than one half of the average pore size of the poroussupport. The buffer layer may have a thickness of about 0.05 to about 10μm, and in one embodiment about 0.05 to about 5 μm.

In an exemplary embodiment of the invention, adequate adhesion andchemical stability may be obtained without a buffer layer. In thisembodiment the buffer layer may be omitted.

The interfacial layer may comprise nitrides, carbides, sulfides,halides, metal oxides, carbon, or a combination thereof. The interfaciallayer provides high surface area and/or provides a desirablecatalyst-support interaction for supported catalysts. The interfaciallayer may be comprised of any material that is conventionally used as acatalyst support. The interfacial layer may be comprised of a metaloxide. Examples of metal oxides that may be used include γAI2O3, SiO₂,ZrO₂, TiO₂, tungsten oxide, magnesium oxide, vanadium oxide, chromiumoxide, manganese oxide, iron oxide, nickel oxide, cobalt oxide, copperoxide, zinc oxide, molybdenum oxide, tin oxide, calcium oxide, aluminumoxide, lanthanum series oxide(s), zeolite(s) and combinations thereof.The interfacial layer may serve as a catalytically active layer withoutany further catalytically active material deposited thereon. Usually,however, the interfacial layer is used in combination with acatalytically active layer. The interfacial layer may also be formed oftwo or more compositionally different sublayers. The interfacial layermay have a thickness that is less than one half of the average pore sizeof the porous support. The interfacial layer thickness may range fromabout 0.5 to about 100 μm, and in one embodiment from about 1 to about50 μm. The interfacial layer may be either crystalline or amorphous. Theinterfacial layer may have a BET surface area of at least about 1 m2/g.

The catalyst may be deposited on the interfacial layer. Alternatively,the catalyst material may be simultaneously deposited with theinterfacial layer. The catalyst layer may be intimately dispersed on theinterfacial layer. That the catalyst layer is “dispersed on” or“deposited on” the interfacial layer includes the conventionalunderstanding that microscopic catalyst particles are dispersed: on thesupport layer (i.e., interfacial layer) surface, in crevices in thesupport layer, and in open pores in the support layer.

The catalyst may be supported on an assembly of one or more finspositioned within the process microchannels. Examples are illustrated inFIGS. 29-31. Referring to FIG. 29, fin assembly 820 includes fins 822which are mounted on fin support 824 which overlies base wall 826 ofprocess microchannel 828. The fins 822 project from the fin support 824into the interior of the process microchannel 828. The fins 822 extendto and contact the interior surface of upper wall 830 of processmicrochannel 828. Fin channels 832 between the fins 822 provide passageways for fluid to flow through the process microchannel 828 parallel toits length. Each of the fins 822 has an exterior surface on each of itssides, this exterior surface provides a support base for the catalyst.With the inventive process, the reactants flow through the fin channels832, contact the catalyst supported on the exterior surface of the fins822, and react to form the product. The fin assembly 820 a illustratedin FIG. 30 is similar to the fin assembly 820 illustrated in FIG. 29except that the fins 822 a do not extend all the way to the interiorsurface of the upper wall 830 of the microchannel 828. The fin assembly820 b illustrated in FIG. 31 is similar to the fin assembly 820illustrated in FIG. 29 except that the fins 822 b in the fin assembly820 b have cross sectional shapes in the form of trapezoids. Each of thefins may have a height ranging from about 0.02 mm up to the height ofthe process microchannel 828, and in one embodiment from about 0.02 toabout 10 mm, and in one embodiment from about 0.02 to about 5 mm, and inone embodiment from about 0.02 to about 2 mm. The width of each fin mayrange from about 0.02 to about 5 mm, and in one embodiment from about0.02 to about 2 mm and in one embodiment about 0.02 to about 1 mm. Thelength of each fin may be of any length up to the length of the processmicrochannel 828, and in one embodiment up to about 10 m, and in oneembodiment about 0.5 to about 10 m, and in one embodiment about 0.5 toabout 6 m, and in one embodiment about 0.5 to about 3 m. The gap betweeneach of the fins may be of any value and may range from about 0.02 toabout 5 mm, and in one embodiment from about 0.02 to about 2 mm, and inone embodiment from about 0.02 to about 1 mm. The number of fins in theprocess microchannel 828 may range from about 1 to about 50 fins percentimeter of width of the process microchannel 828, and in oneembodiment from about 1 to about 30 fins per centimeter, and in oneembodiment from about 1 to about 10 fins per centimeter, and in oneembodiment from about 1 to about 5 fins per centimeter, and in oneembodiment from about 1 to about 3 fins per centimeter. Each of the finsmay have a cross-section in the form of a rectangle or square asillustrated in FIG. 29 or 30, or a trapezoid as illustrated in FIG. 31.When viewed along its length, each fin may be straight, tapered or havea serpentine configuration. The fin assembly may be made of any materialthat provides sufficient strength, dimensional stability and heattransfer characteristics to permit operation for which the processmicrochannel is intended. These materials include: steel (e.g.,stainless steel, carbon steel, and the like); monel; inconel; aluminum;titanium; nickel; platinum; rhodium; copper; chromium; brass; alloys ofany of the foregoing metals; polymers (e.g., thermoset resins);ceramics; glass; composites comprising one or more polymers (e.g.,thermoset resins) and fiberglass; quartz; silicon; or a combination oftwo or more thereof. The fin assembly may be made of an Al2O3 formingmaterial such as an alloy comprising Fe, Cr, Al and Y, or a Cr2O3forming material such as an alloy of Ni, Cr and Fe.

In a further exemplary embodiment, the catalyst may be regenerated. Thismay be done by flowing a regenerating fluid through the processmicrochannels in contact with the catalyst. The regenerating fluid maycomprise hydrogen or a diluted hydrogen stream. The diluent may comprisenitrogen, argon, steam, methane, carbon dioxide, or a mixture of two ormore thereof. The concentration of H₂ in the regenerating fluid mayrange up to about 100% by volume, and in one embodiment from about 1 toabout 100% by volume, and in one embodiment about 1 to about 50% volume.The regenerating fluid may flow from the header 104 through the processmicrochannels to the footer 106, or in the opposite direction from thefooter 106 through the process microchannels to the header 104. Thetemperature of the regenerating fluid may be from about 20 to about 600C, and in one embodiment about 20 to about 400 C, and in one embodimentabout 80 to about 200 C. The pressure within the process microchannelsduring this regeneration step may range from about 1 to about 100atmospheres, and in one embodiment about 1 to about 10 atmospheres. Theresidence time for the regenerating fluid in the process microchannelsmay range from about 0.001 to about 10 seconds, and in one embodimentabout 0.01 second to about 1 second. In one embodiment, the reactionzones in the process microchannels may be characterized by having a bulkflow path. The term “bulk flow path” refers to an open path (contiguousbulk flow region) within the process microchannels. A contiguous bulkflow region allows rapid fluid flow through the microchannels withoutlarge pressure drops. In one embodiment, the flow of fluid in the bulkflow region is laminar. Bulk flow regions within each processmicrochannel may have a cross-sectional area of about 0.05 to about10,000 mm2, and in one embodiment about 0.05 to about 5000 mm2, and inone embodiment about 0.1 to about 2500 mm2. The bulk flow regions maycomprise from about 5% to about 95%, and in one embodiment about 30% toabout 80% of the cross-section of the process microchannels.

Though the exemplary embodiments have been discussed previously withrespect to production of hydrogen peroxide, it is also within the scopeof the present invention to produce other products, such as, withoutlimitation, water, methane, carbon monoxide, carbon dioxide, nitrogen,or a mixture of two or more thereof. The concentration of hydrogenperoxide in the product may range up to about 100% by weight, and in oneembodiment from about 1% to about 100% by weight, and in one embodimentfrom about 5% to about 100% by weight, and in one embodiment from about10 to about 90% by weight, and in one embodiment from about 30% to about90% by weight and in one embodiment about 50 to about 90% by weight. Inan exemplary embodiment, the product comprises hydrogen peroxide andwater, the concentration of hydrogen peroxide being from about 1% toabout 70% by weight, and in one embodiment about 5 to about 50% byweight, and in one embodiment about 10 to about 30% by weight.

The contact time of the reactants with the catalyst within the processmicrochannels may range up to about 500 milliseconds (ms), and in oneembodiment from about 1 ms to about 250 ms, and in one embodiment about10 ms to about 100 ms.

The space velocity (or gas hourly space velocity (GHSV)) for the flow ofthe reactants and product through the process microchannels may be atleast about 10000 hr−1 (normal liters of feed/hour/liter of volumewithin the process microchannels) or at least about 9260 ml feed/(gcatalyst) (hr). The space velocity may range from about 10,000 to about1,000,000 hr−1, or from about 9260 to about 926,000 ml feed/(g catalyst)(hr). In one embodiment, the space velocity may range from about 100,000to about 1,000,000 hr−1, or about 92,600 to about 926,000 ml feed/(gcatalyst) (hr).

The temperature of the reactants entering the process microchannels mayrange from about 20 C to about 200 C, and in one embodiment about 20 Cto about 100 C., and in one embodiment about 20 C to about 50 C.

The temperature within the process microchannels may range from about 50C to about 400 C, and in one embodiment from about 50 C to about 200 C,and in one embodiment from about 100 C to about 200 C.

The temperature of the product exiting the process microchannels mayrange from about 50 C to about 400 C, and in one embodiment about 50 Cto about 200 C, and in one embodiment about 100 C. to about 200 C.

The pressure within the process microchannels may be up to about 100atmospheres, and in one embodiment up to about 10 atmospheres, and inone embodiment up to about 5 atmospheres. In one embodiment the pressuremay range from about 1 to about 10 atmospheres, and in one embodimentfrom about 1 to about 5 atmospheres, and in one embodiment from about 1to about 3 atmospheres.

The pressure drop of the reactants and/or products as they flow throughthe process microchannels may range up to about 100 atmospheres permeter of length of the process microchannel (atm/m), and in oneembodiment up to about 10 atm/m, and in one embodiment up to about 5atm/m.

The reactants entering the process microchannels are typically in theform of a vapor, while the product exiting the process microchannels maybe in the form of a vapor, a liquid, or a mixture of vapor and liquid.The Reynolds Number for the flow of vapor through the processmicrochannels may be in the range of about 10 to about 4000, and in oneembodiment about 100 to about 2000. The Reynolds Number for the flow ofliquid through the process microchannels may be about 10 to about 4000,and in one embodiment about 100 to about 2000.

The heat exchange fluid entering the heat exchange channels may be at atemperature of about 20 C to about 200 C, and in one embodiment about 20C to about 100 C. The heat exchange fluid exiting the heat exchangechannels may be at a temperature in the range of about 50 C to about 400C, and in one embodiment about 100 C. to about 200 C. The residence timeof the heat exchange fluid in the heat exchange channels may range fromabout 1 to about 1000 ms, and in one embodiment about 10 to about 500ms. The pressure drop for the heat exchange fluid as it flows throughthe heat exchange channels may range up to about 100 atm/m, and in oneembodiment up to about 10 to atm/m, and in one embodiment up to about 5atm/m, and in one embodiment from about 1 to about 5 atm/m. The heatexchange fluid may be in the form of a vapor, a liquid, or a mixture ofvapor and liquid. The Reynolds Number for the flow of vapor through theheat exchange channels may be from about 10 to about 4000, and in oneembodiment about 100 to about 2000. The Reynolds Number for the flow ofliquid through heat exchange channels may be from about 10 to about4000, and in one embodiment about 100 to about 2000.

The conversion of O₂ may be about 10% or higher per cycle, and in oneembodiment about 30% or higher, and in one embodiment about 50% orhigher per cycle. The conversion of H₂ may be about 10% or higher percycle, and in one embodiment about 30% or higher, and in one embodimentabout 50% or higher per cycle. The yield of hydrogen peroxide may beabout 10% or higher per cycle, and in one embodiment about 30% orhigher, and in one embodiment about 50% or higher per cycle. In oneembodiment, the conversion of O₂ is at least about 30%, the conversionof H₂ is at least about 30%, and the yield of hydrogen peroxide is atleast about 30% per cycle. Unlike conventional reaction vessels for thedirect production of hydrogen peroxide from O₂ and H₂ which have to takeinto account the possibility of explosions as a result of the use of O₂and H₂, the possibility of such explosions with the inventive process isof less concern. This is believed to be due to the relatively briefcatalyst contact times employed in the process microchannels, the addedcooling provided by the heat exchanger, and the dimensions of themicrochannels which make them effective flame arresters reducing orpreventing the propagation of combustion reactions and flames that wouldnormally lead to explosions and/or detonations.

The exemplary embodiments of the present invention may utilizemanifolds, as discussed briefly above, to transition to and from themicrochannel. The following is a more thorough explanation of themanifolds for use with the present invention.

This section will describe manifold physics important to manifold designand begin to describe how M2M manifolds differ from larger scalemanifold systems. The following section will describe experimentallyobtained M2M parameters relevant to the invention. Fried and Idelchik in“Flow resistance: A design guide for engineers,” Hemisphere PublishingCorporation, 1989, and Idelchik Dekker in “Fluid Dynamics of IndustrialEquipment Flow distribution Design Methods”, Hemisphere PublishingCorporation, 1991 have described means of designing conventionally-sizedpipe and duct manifolds with large cross-sectional area connections.These ducts are characterized by large hydraulic diameters for themanifold and the connecting channels. Because of the large hydraulicdiameters even small specific velocities or mass flux rates can lead toturbulent Reynolds numbers that dominate the friction losses and theother manifold physics. In M2M manifolds, the manifold channels arebuilt into the layers of the device, so they often have hydraulicdiameters on the same order of the connecting channels, much smallerthan many conventional pipe or duct based manifold systems. Due to theM2M manifold having small hydraulic diameters, fairly large specificvelocities or mass flux rates can have transition and even laminar flowcharacteristics which can affect flow distribution in ways differentfrom fully turbulent manifolds.

In large pipe and duct manifolds the relative cross-sectional areas ofdelivery manifolds compared to the connecting channels are often limitedby the size of the delivery manifold. As the delivery manifold'shydraulic diameter is sized to lower the pressure drop of the system,its cross-sectional area is typically larger than the interface with theconnecting channel to make fabrication of the connection (welding,joining or flanging) easier. For this reason the connection to manifoldcross-sectional area ratio of the connecting channel interface to thedelivery manifold is equal to or less than one for most cases. For M2Mmanifolds, the connection from the manifold to the connecting channelsis fabricated in the same manner as the connecting channels, so thefabrication limitations of size of the connecting channel opening todelivery manifold is taken away. The in plane fabrication methods couldallow one or more connecting channels with a manifold interface that hasa larger area than the manifold, and its connection to manifoldcross-sectional area ratio could be larger than unity.

For large pipe and duct manifolds the effect of friction losses in thelength of the manifold directly adjacent to the connecting channelinterface is usually negligible because the length over hydraulicdiameter are on the order of unity (L/D ˜1). Because of the small L/Dratio, one only accounts for momentum compensation, discussed later, inthat zone. As discussed in the previous paragraph, the length of the M2Mmanifolds adjacent to the connecting channel interfaces can be large dueto channel geometry resulting in length over diameter ratios much largerthan unity, so that one can't always assume that the friction losses canbe ignored.

To design a manifold for a set of connecting channels, it is useful touse one-dimensional coefficients to describe complex three-dimensionalflow resistances wherever possible, and this analysis will use equationssimilar to those used by Fried and Idelchik. Using one-dimensionalcoefficients allows a designer to solve for local momentum balances andmass continuity in a manner akin to electrical circuit analysis, whichis very useful when evaluating design changes for flow distribution. Byusing one-dimensional coefficients, the source of major flowmaldistributions can be identified and manifold physics compensated forin ways discussed later in the patent. To design using the circuitanalysis, the representative equations that need to be solved aredefined. This description will be illustrated using a case of threeconnecting channels, shown in FIG. 1A1. The channels have three manifoldconnecting areas, where the cross-sectional areas are A_(c,i) [m²]. Theconnecting channel cross sectional areas are A_(cc), [m²]. The localmass flux rates G [kg/m²/s] and the local, absolute static pressures P[Pa] are shown. A_(c,i) [m²] (can be a gate, or any other orificedesign), which may or may not be different than the channel area(A_(cc), [m²]). The cross-sectional area in the manifold can change inthe direction of flow, as shown in FIGS. 1A1 and 1B1 with changingwidth.

In many embodiments of the present invention, distribution is preferredto be equal, or nearly so, in all connecting channels. However, itshould be noted that a small amount of flow maldistribution may beacceptable and not noticeable from the overall device performance. Insome embodiments, the amount of acceptable flow maldistribution may beequivalent to a quality index factor of 5%, 10%, or up to 30%. By equal,is meant that one of the following conditions hold:

Constant mass flow rate, m [kg/s]: all connecting channels have the samecross-sectional area, A_(cc) [m²], as a design basis. This leads to a Q₁value of zero. This is the basis for the channels in FIGS. 1A1 and 1B1.

Constant mass flux rate, G: for cases when the connecting channels havedifferent channel sectional areas, but the total contact time is thesame. This leads to a Q₂ value of zero. For cases when all crosssectional areas are equal, the constant mass flux rate simplifies toconstant mass flow rate case. For the design of the manifold andconnecting channels, a set of equations are solved to determine massflux rates and pressures.

The momentum balance from the inlet to the outlet of connecting channeli in FIGS. 1A1 and 1B1 is

$\begin{matrix}{{\Delta \; P_{{cc},i}} = {{P_{i,c} - P_{i,o}} = {r_{cc}\frac{G_{c,i}^{2}}{2\rho}}}} & (1)\end{matrix}$

wherer_(cc) [−]=Connecting channel flow resistanceG_(c,i) [kg/m²/s]=Connecting channel i's mass flux rate, based uponA_(cc).P_(i,c) [Pa]=Pressure of the header manifold connection plane centerP_(i,o) [Pa]=Pressure of the footer manifold connection plane centerΔP_(cc,i) [Pa]=Connecting channel i pressure differentialρ [kg/m³]=Density of fluidA resistance function representing several flow resistance terms may beused instead of a series of individual momentum balances for theconnecting channels, such as friction losses, cross-sectional areachanges and other losses. The resistance can be a function of mass fluxrate, geometry, molar composition changes, and temperature changes amongothers. Either resistance or a series of individual momentum balancescan be used, and resistance is used here to simplify the system. Aresistance function is obtained by taking the sum of the connectingchannel pressure drops for a range of flow rates and dividing eachpressure drop by its representative head value (G_(c,i) ²/2/□), thencorrelating by the head value.

To generate pressure drops in the connecting channels, the pressuredrops have to be calculated from known correlations or estimatedexperimentally. Friction pressure losses for straight sections ofconnecting channels can be calculated using the Fanning frictionfactors. Sources of Fanning friction factors and their manner of useinclude Rohsenow et al [“Handbook of Heat Transfer”, 3^(rd) ed. McGrawHill, 1998] for a wide range of channel geometries, and Shah and London[“Laminar Flow forced convection in ducts,” Supplement 1 to Advances inHeat Transfer, Academic Press, new York, 1978] for laminar flows. Careshould be placed in using appropriate Reynolds numbers, channel geometryfactors (such as aspect ratios), and hydrodynamic dimensionless lengths(x⁺=L/D/Re, where L is the section's length, D is channel's hydraulicdiameter and Re is the channel's Reynolds number) for laminar flows forthe Fanning friction factor. If friction factors aren't available forthe connecting channels considered, experimental values can be obtainedfrom fabricated channels fitted with pressure taps placed in welldeveloped flow zones. If the connecting channels have pressure dropsfrom sudden changes in cross-sections or changes in plane, Fried andIdelchik [“Flow resistance: A design guide for engineers,” HemispherePublishing Corporation, 1989] have a number of equations and references.

To set a perfect distribution, solving for the G_(c,i) then results in

$\begin{matrix}{G_{c,i} = {G_{c,{perf}} = \sqrt{2\rho \frac{\Delta \; P_{{cc},i}}{r_{cc}}}}} & (1)\end{matrix}$

G_(c,perf) [kg/m²/s]=Connecting channel perfect mass flux rate, i.e. thedesign point.If the fluid is incompressible, the fluid density is an average of theconnecting channel conditions. If the fluid is an ideal gas and theconnecting channel pressure drop is less than 10% of the inlet pressure,the density can be approximated by the local average pressure,temperature and molecular weight of the gas as follows

$\begin{matrix}{G_{c,i} = {G_{c,{perf}} = \sqrt{\frac{P_{i,c}^{2} - P_{i,o}^{2}}{r_{cc}}\left( \frac{{Mw}_{e}}{{RT}_{e}} \right)}}} & (2)\end{matrix}$

where we use an equivalent set of parameters to describe changingconnecting channel conditions:Mw_(e) [kg/gm-mole]=Average mole fraction for the gas in the connectingchannelR [J/gm-mole/K]=Gas constantT_(e) [K]=Average gas temperature

The following six factors characterize the system:

-   -   1. The outlet pressure profile, P_(i,o) for i from 1 to N total        channels    -   2. Either one of the following:        -   a. The inlet pressure of the macro manifold, P_(macro)        -   b. Or the inlet pressure of the M2M manifold, Pin        -   c. Or the inlet manifold mass flux rate, G₁.    -   3. Connecting channel geometries (heights, widths, lengths)    -   4. Connecting channel conditions (temperature, mole fractions,        adding/losing fluids)    -   5. Manifold geometries    -   6. Manifold conditions (temperature)

With the above information and the three-channel (N=3) system in FIG.1A1, there are seventeen (6N−1) unknowns for a header system:

-   -   Six (2N) header pressures (P_(1,A), P_(1,B), P_(2,A), P_(2,B),        P_(3,A), P_(3,B))    -   Three (N) connecting channel inlet pressures (P_(1,c), P_(1,c),        P_(1,c))    -   Three (N) header M2M manifold mass flux rates at the connection        inlet (G_(1,A), G_(2,A), G_(3,A))    -   Two (N−1) header M2M manifold mass flux rates at the connection        outlet (G_(1,B), G_(2,B))    -   Three (N) connecting channel mass flux rates (G_(c,1), G_(c,2),        G_(c,3))

The exact position of the pressures A and B for the manifold are definedas follows: For the header, Position A at the manifold connection i isdefined as the intersection of the manifold channel axis and the planemade by the manifold connection i's wall closest to the header manifoldinlet. The header Position B at the manifold interface i is defined asthe intersection of the manifold channel axis and the plane made by themanifold connection i's wall farthest from the header manifold inlet.

For the footer, Position A at the manifold connection i is defined asthe intersection of the manifold channel axis and the plane made by themanifold connection i's wall farthest from the footer manifold outlet.For the footer, Position B at the manifold connection i is defined asthe intersection of the manifold channel axis and the plane made by themanifold connection i's wall closest to the footer manifold outlet. Theplane “made” by the manifold's connection wall is a plane, perpendicularto the central axis of the manifold, that intersects an edge of themanifold connection.

The last mass flux rate in the M2M manifold header is zero, because themanifold ends.

G_(3,B)=0  (1)

The 6N−1 unknowns are linked by the following 6N−1 equations:

-   -   Momentum balance for connecting channel i (N total), from        equation (9)    -   Momentum balance between connecting channel i and the manifold        (N total), also known as the “turning loss”, the resistance to        flow between the manifold and the manifold interface (can be a        gate or a grate):

$\begin{matrix}{{\left\lbrack \frac{P_{i,A} + P_{i,B}}{2} \right\rbrack - P_{i,C}} = {{\zeta \left( {\frac{G_{cc}A_{c,i}}{G_{i,A}A_{M,A,i}},\frac{A_{c,i}}{A_{M,A,i}}} \right)}\frac{G_{i,A}^{2}}{2\rho_{{M\; c},i}}}} & (2)\end{matrix}$

-   -   where    -   A_(c,i) [m²]=Cross-sectional area of the connecting channel i,        at the manifold interface (not necessarily the area of the        connecting channel)    -   A_(M,A,i) [m²]=Cross-sectional area of the manifold at        connecting channel i    -   ξ [dimensionless]=Turning loss function from the M2M manifold to        the connecting channel    -   ρ_(Mc,i) [kg/m³]=Average density of the fluid between the        manifold and connecting channel i

The turning losses can be considered as part of a connecting channel'stotal pressure drop and can have a strong effect on flow distribution.The values of the turning loss are positive for the header, and canpossibly be positive or negative for the footer, resulting in a pressuredrop for the former and a net static pressure increase for the latter.If the manifold geometry and manifold connection geometry affect uponthe turning loss is well understood, such as large pipes, you can use acorrelation for the turning loss as those described in Fried andIdelchik [“Flow resistance: A design guide for engineers,” HemispherePublishing Corporation, 1989]. If that isn't an option, another means ofobtaining the turning loss coefficient □ for specific manifold geometryis obtaining from experiment the pressures, upstream mass flux rate, theaverage density and solving for □ using equation 14. The header manifoldpressure at the interface can be used instead of the average of P_(i,A)and P_(i,B) in equation (14), as it represents the average pressure inthe manifold across the manifold connection interface.

-   -   Mass continuity equation between connecting channel i and the        manifold (N total)

A _(M,A,i) G _(i,A) −A _(M,B,i) G _(i,B) =A _(cc) G _(c,i)  (1)

-   -   where    -   A_(M,B,i) [m²]=Cross-sectional area of the manifold at        connecting channel i, downstream of the connecting channel    -   Mass continuity in the manifold between connecting channels i        and i+(N−1 total)

A _(M,A,i+1) G _(i+1,A) =A _(M,B,i) G _(i,B)  (2)

-   -   Manifold momentum balance at the connecting channel i, which        includes friction losses and momentum compensation terms (N        total)

$\begin{matrix}{{P_{i,A} - P_{i,B}} = {{{{k_{M}\left( {\frac{A_{M,B,i}G_{i,B}}{A_{M,A,i}G_{i,A}},{{Re}\left( \frac{G_{i,A} + G_{i,B}}{2} \right)}} \right)}\left\lbrack {G_{i,B}^{2} - G_{i,A}^{2}} \right\rbrack}\frac{1}{\rho_{M,i}}} + {4{f\left( {{Re}\left( \frac{G_{i,A} + G_{i,B}}{2} \right)} \right)}{\frac{L_{i,c}}{D_{i}}\left\lbrack \frac{G_{i,A} + G_{i,B}}{2} \right\rbrack}^{2}\frac{1}{2\rho_{M,i}}}}} & (3)\end{matrix}$

-   -   where    -   D_(i) [m]=Hydraulic diameter of the manifold at connection i    -   f [dimensionless]=Fanning friction factor for the manifold    -   k_(M) [dimensionless]=Momentum compensation factor    -   L_(i,c) [m]=Length of the connecting channel opening in the        manifold at connection channel i    -   ρ_(M,i) [kg/m³]=Average density of the fluid in the manifold at        connection channel i

The momentum compensation coefficient k_(M) always has a positive valuein the header, which can lead to leading to an increase in staticpressure across the manifold connection if that effect is stronger thanfriction losses. Average mass flux rates based on the upstream anddownstream values are used for this analysis. The effect of momentumcompensation can vary the pressure profiles in the header and footergreatly. If the manifold geometry and manifold connection geometryaffect upon the momentum compensation coefficient k_(M) is wellunderstood, such as large pipes, you can use correlation for the turningloss as those described in Pigford et al (“Flow distribution in pipingmanifolds”, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, v. 22,INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, pp. 463-471, 1983). If thatisn't an option, another means of obtaining the momentum compensationcoefficient k_(M) for specific manifold geometry is obtaining fromexperiment the pressures, upstream and downstream mass flux rates, theaverage manifold density and solving for k_(M) using equation (17).

-   -   Manifold momentum balance upstream of connecting channel i (N        total)

$\begin{matrix}{{P_{i,B} - P_{{i + 1},A}} = {\frac{4{f\left( {{Re}\left( \frac{G_{i,A} + G_{{i - 1},B}}{2} \right)} \right)}L_{u,i}}{D_{u,i}}\frac{\left( \frac{G_{i,A} + G_{{i - 1},B}}{2} \right)^{2}}{2\rho_{u,i}}}} & (1)\end{matrix}$

-   -   where    -   D_(u,i) [m]=Average hydraulic diameter of the manifold's        upstream section prior to connection channel i    -   L_(i,c) [m] Length of the connecting channel opening in the        manifold at connection channel i    -   ρ_(u,i) [kg/m³]=Average density of the fluid in the manifold        upstream connection channel i        Thus, there are 6N−1 equations for 6N−1 unknowns. These        nonlinear equations can be solved simultaneously using a number        of solution strategies. If the manifold channel width is        constant in the manifold, the equations simplify. Note that, for        gases, the local average density is a function of local        pressure.

A similar set of 6N−1 equations can be written for the footer manifold.The direction of manifold flow is from A to B. The footer G_(1,A) valueis zero, as it is there is no flow prior to the first manifoldconnection. The manifold connection to manifold pressure drop inequation (14) would change the sign of the equation (14)'s right handside, along with the head term's mass flux basis to G_(i,B). The valueof the footer turning loss coefficient in (14) would be dependent uponG_(i,B), also. The footer manifold pressure at the interface can be usedinstead of the average of P_(i,A) and P_(i,B) in the footer version ofequation (14), as it represents the average pressure in the manifoldacross the manifold connection interface. The sign on the right handside of equation (15)'s continuity equation would change to negativewhile the continuity equation in (16) would be the same. Equation (17)'sform is the same, leading to a net decrease in static pressure from A toB caused by the combined friction and momentum compensation losses. Theonly change to equation (17) is that the ratio

$\frac{A_{M,B,i}G_{i,B}}{A_{M,A,i}G_{i,A}}$

is inverted so the footer manifold mass flow rate ratio is correct forthe footer. Equation (18) stays as is for the footer.

For footer Z-manifolds and footer L-manifolds the number order ofmanifold connection i increases follows in the same direction as theheader. The direction of G can be in the opposite direction of theheader for U-manifolds. This means the manifold interface numberingscheme goes in the opposite direction of the header.

M2M Manifold Physics

The flow of fluid takes the path of least resistance to leave amanifold. If the connecting channels have large pressure drop at thedesign flow rate compared to the manifold physics described in the lastsection, the flow distribution in the connecting channels will be mostlyequivalent and sophisticated manifold designs become less necessary. Ifthe connecting channels pressure drop at the design flow rate is lowcompared to the manifold pressure drops, then depending on the manifoldheader and footer pressure profiles there is potential for poor flowdistribution. The manifold physics versus the connecting channelpressure drop must be balanced to obtain the necessary connectingchannel flow distribution for a given manifold.

For low relative flow rates, friction losses dominate the staticpressure profiles in the manifolds because the small head values don'tgive rise to large turning losses or momentum compensation staticpressure changes. Examples of such cases include lab-on-a-chipanalytical devices and reactions with relatively long contact times. Todistribute flow to microsecond contact time reactors and fast liquidphase reactions, a manifold can potentially see very high mass fluxrates or velocities, even at low Reynolds numbers. These large headvalues can give rise to not only large friction losses but alsosubstantial turning and momentum compensation static pressure changes.The latter two pressure changes can strongly affect flow distribution inmanifolds.

Momentum compensation refers to the change in manifold static pressurebased on flow leaving and entering a manifold from a connecting channel.Momentum compensation increases the header static pressure each timefluid leaves the header to join the connecting channel, and it ispossible that the static pressure rise associated with momentumcompensation can be larger than friction losses at the connection. Therise in static pressure can be thought of as the means of “pushing” thefluid into the connecting channel. Momentum compensation acts todecrease static pressure in the footer, with the loss in static pressureattributed to accelerating the connecting channel's flow in thedirection of the manifold flow. The combination of momentum compensationand friction losses can greatly decrease the footer static pressure inthe direction of M2M footer manifold flow.

Momentum compensation is a function of the mass flow rate ratio, theratio of the manifold flow rates just downstream to just upstream of adistribution point, and the flow regime of the fluid in the manifold.The mass flow rate ratio ranges from zero to one, and the mass flow rateratio is the ratio of the downstream to upstream mass flow rates for theheader and the ratio of the upstream to downstream flow rates for thefooter. Microchannel M2M manifolds with high enough heads can seemomentum compensation static pressure increases large enough to increasethe static pressure in the header despite frictional static pressurelosses, resulting in an increase of the static pressure driving forcefor flow to the connecting channels in the direction of flow. An exampleof the static pressure increase is seen in FIG. 2A1, where the staticpressures in a header or footer calculated for a large M2M Z-manifoldsystem based upon turbulent pipe turning loss and momentum compensationcoefficients. Channel 1 is the first connecting channel that the headermanifold interacts with, while channel 19 is the last connecting channelthe footer interacts with. The momentum compensation effect in theheader drives the static pressure up with increasing channel number(direction of flow), despite frictional losses, while the combinedfrictional and momentum compensation losses in the footer drive thestatic pressure down with increasing channel number. The resultingpressure profile drives more flow to the higher number channels due tothe larger pressure differential driving force with the same connectingchannel flow resistance.

Experimental data for the microchannel header momentum compensationcoefficients versus local average Reynolds numbers are plotted in FIG.2B1. The solid shapes show different manifold mass flow rate ratios(downstream over upstream). The header manifold mass flow rate ratio ofzero represents the last channel in the header, while one halfrepresents the second to last channel, assuming equal mass flow in bothconnecting channels. The value of the ratio increases as the channelsincrease in number from the end of the header manifold, up to a valueapproaching unity. As can be seen, the turning losses show a dependenceupon Reynolds number, as the headers see values in the laminar (Re<2200)to transition (2200<Re<4000-5000). For many curves a change in the M2Mheader momentum compensation coefficient can be seen at the transitionfrom laminar to transition flow. The M2M header momentum compensationcoefficient values tend to be on the same order or higher than seen inpipes from Pigford et al (“Flow distribution in piping manifolds”,INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, v. 22, INDUSTRIAL &ENGINEERING CHEMISTRY RESEARCH, pp. 463-471, 1983) (values of 0.4-0.7).These M2M header momentum compensation values have experimentally leadto increases in header static pressure, even at inlet Reynolds numbersbelow 1000.

The average header Reynolds number is used as a basis of the M2Mmomentum compensation coefficient because this coefficient is obtainedfrom the experimental change in the static pressure from the beginningof the connecting channel to the exit by subtracting the frictionalpressure drop from it, which is based upon the average Reynolds numbers.As the connecting channel openings can be quite long in the direction offlow in the M2M manifold and spaced close together, the pressure canchange appreciably in the manifold, as mentioned in the previoussection.

The Reynolds number in the header can change appreciably in an M2Mmanifold due to its small hydraulic diameter and large mass flux ratesneeded to supply fast reactions, high effectiveness heat exchangers andother unit operations aided by microchannel architecture. Some preferredembodiments have operational contact times (contact times through theconnecting channels) of fifty milliseconds and less, and some havecontact times of ten milliseconds and less. The value of the Reynoldsnumbers in preferred embodiments can vary across the M2M manifold fromturbulent flow, to transition flow to laminar flow; in other preferredembodiments it can vary from transition flow to laminar flow. In otherpreferred embodiments it can vary from transition flow to turbulentflow. For M2M manifolds where the flow regime changes, the frictionlosses and the M2M momentum compensation losses, the latter seen in FIG.2B1, change with it. These flow regime changes affect the pressureprofiles in the M2M manifold and can contribute to poor flowdistribution.

The turning loss is defined as the static pressure change the connectingchannel pays to divert the flow to and from the manifold to theconnecting channel. The turning loss is a function of

-   -   1. The cross-sectional area ratio of the connecting channel        interface over that of the manifold;    -   2. The local ratio of the mass flow rate of the connecting        channel to that of the highest manifold mass flow rate at the        connection, upstream or downstream; and    -   3. The shape of the manifold cross section. For rectangular        cross sections, the shape is quantified with the manifold aspect        ratio.

For constant values of the cross-sectional area of both the manifold andthe connecting channel interface, the header turning loss tends to behigher for the connecting channels closest to the header entrance thanto those farther downstream. This change in the turning loss withposition in the manifold is based upon the change in the manifold head:The head value decreases in the direction of header flow, so diverting afraction becomes less energy intensive.

FIG. 2C1 shows the experimental values of the M2M header manifoldturning loss coefficient measured in a microchannel M2M header manifoldwith an grate interface to manifold area ratio of 0.09, plotted versusthe connecting channel to upstream M2M header manifold mass flow rateratio of the grate interface to the manifold just upstream of the grateinterface. Also in FIG. 2C1 are the turning loss coefficients for largedimension manifold from Fried and Idelchik (“Flow resistance: A designguide for engineers,” Hemisphere Publishing Corporation, 1989) shown insolid line. In general, microchannel M2M (macro to micro) turning losscoefficients follow a similar trend to that of the Fried and Idelchikturning loss coefficients: the values increase with decreasingconnection to manifold cross-sectional area ratio. This implies that alarger pressure drop is needed to turn manifold flow into a smallerconnecting channel opening. The turning loss coefficient increases withincreasing connecting channel to upstream M2M header manifold mass flowrate ratio (or increase with position down the manifold, 0 being for thefirst channel, 1 for the last channel). However, the turning losses,based upon the product of the manifold head upstream of the grateinterface and the turning loss coefficient, are higher for the firstchannel in the header than for the last channel if the connection tomanifold cross-sectional area ratios are constant. This is because theincrease in the turning loss coefficient's value with connecting channelto upstream M2M header manifold mass flow rate ratio approaching one(i.e. the end of the header) isn't as large as the decrease in themanifold head (G²/2/□) as the manifold loses mass flow rate

The microchannel turning losses in FIG. 2C1 are a factor of 2 to 5higher than turbulent pipe values, making the turning losses even higherthan pipes for connecting channel to upstream M2M header manifold massflow rate ratios greater than 0.2. The manifold aspect ratio (largestside of the rectangle over the smallest) of the M2M manifold causes thehigh header turning losses. M2M manifold channel heights are constrainedby stacking limitations, as there is often a limited amount of heightavailable between repeating layers. Faced with the restriction ofchannel height, the M2M manifold can increase its width to increase theoverall manifold cross-sectional area for flow. By increasing themanifold cross-sectional area for flow, one can lower both frictionallosses and momentum compensation static pressure changes. By increasingthe cross-sectional area, the local manifold head is also decreased. Asthe M2M manifold channel aspect ratio increases, the flow turning fromthe manifold into the connecting channel sees increasing shear stressfrom the channel walls above and below. These wall shear stressesincrease the turning loss pressure drop with increasing M2M manifoldaspect ratio, where circular pipes and nearly square cross-sectionedducts have much less of this. For example, the M2M manifold channelaspect ratio for the M2M turning loss coefficient in FIG. 2C1 is roughly16:1.

For the footer turning losses, there is further interesting phenomena.FIG. 2D1 shows the negative values of the experimental M2M footerturning loss coefficients for the footer manifold plotted versus thelocal connecting channel connecting channel to upstream M2M headermanifold mass flow rate ratio of the connecting channel to that of thehighest manifold flow rate at the connection, downstream of the footerconnection. The M2M footer turning loss coefficients in FIG. 2D1 are fora connecting channel interface to manifold area ratio of 0.09 and an M2Mmanifold aspect ratio of 16:1, and the large manifold numbers from Friedand Idelchik (“Flow resistance: A design guide for engineers,”Hemisphere Publishing Corporation, 1989) for the same connection tomanifold cross-sectional area ratio are plotted. The negative valuefooter turning coefficients for the pipe manifolds (from Fried andIdelchik) show a monotonic increase in the footer turning losscoefficient with increasing connecting channel to upstream M2M headermanifold mass flow rate ratio. These negative footer turning losscoefficients in FIG. 2D1 for both cases means that these coefficientshave a negative value, so when the footer turning loss coefficient ismultiplied by the manifold head downstream of the connecting channelthere will be a net increase in the static pressure from the connectingchannel outlet to the manifold. This static pressure increasecompensates for the static pressure header turning loss to some degree.The footer turning loss coefficient for the 16:1 M2M manifold aspectratio is a factor of two or three smaller than that of the Fried andIdelchik footer turning loss coefficients. The M2M manifold aspect ratiois probably a strong contributor to the difference in footer turningloss coefficient values, with wall shear stress lowering the net staticpressure increase compared to the large manifold system in Fried andIdelchik.

In summary, the experimental M2M manifold momentum compensation and M2Mmanifold turning losses coefficients diverge strongly in value fromreported values used for large pipe and duct systems, mostly due to theeffect of large M2M manifold aspect ratio manifold channels. These largeM2M manifold aspect ratios are needed to slow down the velocities in theM2M manifold, which in turn decrease local head values which drive thefriction, turning and momentum effects. To avoid making larger M2Mmanifold aspect ratios than the values described above and theirassociated turning losses, a wide M2M channel can be split into severalsmaller manifolds of smaller widths that distribute flow to a fractionof the total connecting microchannels. These smaller manifolds arereferred to as sub-manifolds. If the coefficients of momentumcompensation and turning losses are well understood for a given M2Mmanifold aspect ratio in a M2M manifold, it is possible to manipulatethe manifold and connecting channel cross-sectional areas to tailor theturning losses to compensate for other manifold static pressure changesfrom friction losses and momentum compensation static pressure changes.By tailoring the turning losses in a manner that will make the drivingforce for flow equal across the connecting channels despite the otherchanges in manifold pressure profiles, it is possible to reach anequivalent distribution of flow in each connecting channels. From thisdesire for controlling turning losses came the invention of variablecross-section grates and gates. Sub-manifolds, grates and gates arediscussed in the next section, in addition to other novel means ofcontrolling flow distribution in M2M manifolds.

M2M Distribution Layers

Flow into the M2M of a microdevice is usually routed through a largepipe, tube, or duct. Each large pipe or duct may further serve toconnect multiple microdevices operating in parallel. Flow distributionoccurs through multiple layers. One large pipe or duct meters flow toone or two or more microdevices. Once flow enters the microdevice, itmay then be further segregated into submanifolds. Each submanifoldserves to distribute flow to at least two or more connecting channels.Flow may then be further divided within a connecting channel intosubchannels. Subchannels may be formed, for example, by the use of fins(either inserted before or after bonding) or integral (such as thoseformed from the laminae or shims). Flow in one microchannel may bedivided into at least two subchannels and in some embodiments, 10 to 100subchannels.

Improved Distribution in Micro-to-Macro Manifolds

As discussed in the previous section, when the cross-sectional arearatio of the connecting channel to the manifold becomes small and theM2M manifold aspect ratio is high, the effect of turning pressure lossesin manifolds can be dramatic for the first channel in a header manifoldor the last channel in a footer manifold. If an M2M manifold distributesflow to a large number of connecting microchannels, the manifold widthcould be increased to slow the mass flux rate enough to avoid largeturning losses. This in turn decreases the connection to manifoldcross-sectional area ratio and increases the M2M manifold aspect ratioresulting in increasing turning losses. The turning losses add to theoverall connecting channel pressure drop (which includes frictional andother losses) and can lead to poor flow distribution. This is seen inmicrochannel process technology (MPT) devices in which large flows aredistributed across long distances to individual microchannels.

Splitting a larger M2M manifold into cascaded layers of smaller parallelM2M manifolds, each of which feed two or more connecting microchannelsor one large M2M manifold aspect ratio connecting microchannel canimprove flow distribution. A manifold can be split into separatemanifolds with walls, with each sub-manifold handling a fraction of thetotal flow. This change increases the connection to manifoldcross-sectional area ratio and lowers the cross-section's M2M manifoldaspect ratio, making turning losses lower. FIG. 3A1 shows a M2MZ-manifold split into two separate M2M sub-manifolds 312, 314. Thesub-manifold includes length in addition to the distribution zone oflength LM2M. This additional length can be used to tailor the pressuredrop for the sub-manifold.

The width of the sub-manifold section between a macro manifold and aconnecting channel distribution section can be changed to affect thesub-manifold's flow resistance. FIG. 3B1 shows a sub-manifold design foran L-manifold with two sub-manifolds and connecting channels ofequivalent flow resistance. The width of the sub-manifold with thelonger upstream flow path, w₂, is wider than the path for thesub-manifold with the shorter upstream flow path, w₁. This difference inupstream widths allows a means of decreasing the flow resistance for thelonger flow path sub-manifold and increasing the flow resistance of theshorter flow path sub-manifold so that both sub-manifolds can meter thesame amount of total flow. A similar method to this L-manifold'ssub-manifold width design can be used for U-manifolds, which have asimilar problem matching pressure drops in multiple sub-manifolds withthe added burden of matching the total flow resistance betweensub-manifold that include headers and footers of differing lengths. Anadditional benefit can be that the walls separating sub-manifolds canact as pillars of mechanical support to handle loads applied the wallshims directly above and below in the direction of stacking.

Channel walls often need some material to hold the ends together in away that avoids creating long and dangling features that could shiftposition during fabrication and/or operation. FIG. 3C shows an examplein which one or more shims whose microchannels end in a bar 37perpendicular to the channels' axes, signaling the end of themicrochannel. In this example, the bar 37 forms a grate that defines oneside of a manifold 370. The plane created by the bar 37 and the openspace in the adjacent channel is the connecting channel plane exit orentrance. This connecting channel plane design is similar to thatillustrated by Golbig et al and discussed in Example 1, except theconnecting channel in Golbig's stays in the plane under 37 and doesn'textend into the plane of 37.

An example is shown in FIG. 3D1. In this example, each crossbar 39(upper shim), 38 (lower shim) forms a portion of the grate. The opening36 created by the differences in the shim channel's ends creates aninterface for fluid flow between the microchannels 35 and the M2Mmanifold.

In some embodiments, it is better to have more of the M2M zone availablefor flow to lower the M2M mass flux rates, which in turn could lower themomentum compensation static pressure changes, turning and frictionlosses. FIG. 3D1 shows the “grate” concept for a single sub-manifold.For the header 384, fluids flows in the M2M and turns into and over theoutstretched “grate” 38, entering the interface channel 36 created bythe lower shim 38 and the upper shim 39 that marks the end of themicrochannel. The flow then leaves the interface and enters themicrochannels 35. The flow distribution can be tailored by varying thedegree the “grate” sticks out into the manifold over the length of a M2Mmanifold and also by varying the width of the opening 36 under thecrossbar 33. The design in FIG. 3D has been tested in a flowdistribution test device.

A “gate” connects an M2M manifold to two or more connectingmicrochannels. Gate features can help distribute flow with a lowerpressure drop than a conventional orifice, which seeks to obtain flowdistribution by making all the flows pay an equally large suddenexpansion and contraction pressure drop. The gate uses turning losses tometer flow to a connecting channel, set of connecting channels, orsubmanifold, and does so by varying the gate cross-sectional area. Thistailoring of the turning loss allows the gate to compensate for changesin the manifold pressure profiles so that the connecting channelpressure drops are equivalent. Gates also use friction losses, expansionand other distribution features to add back pressure. By varying gatecross-sectional area it is possible to add back pressure to or removebackpressure from a sub-manifold in a larger manifold cascade as a meansof controlling overall sub-manifold flow resistance.

In L-manifolds, orifice gates 31 in the connecting channel smooth outdistribution by forcing flow through a narrowed opening in the entranceof the connecting channels. FIGS. 3E1 and 3F1 show an example of a gate,with an opening in the gray shim to let in flow through the wall createdby the stacking of two or more shims. This “gate” is an extension of the“grate” design in that it brings an end to the connecting microchannelsin shim geometry and allows access to the microchannels from the M2Mmanifold.

Gates and grates use the turning losses to equalize the static pressureprofiles at the connecting channel interfaces, but the manner in whichthey do so are different from orifices. Orifices use constant smallmanifold connection cross-sectional areas to impose large flowresistances for each connection, and incur large operating costs in theform of higher overall pressure drops. The inventions described in gatesand grates use two or more openings of varying cross-sectional area touse the naturally occurring turning losses to overcome the manifoldstatic pressure profiles caused by manifold physics. In Example 3, thegate openings in the direction of flow decrease in size to compensatefor the larger turning losses for the first opening and the increasedstatic pressure driving force at the last two gates caused by momentumcompensation. These gate sizes help control flow without the largepressure drops associated with orifice flow resistance. For gates andgrates, the preferred value of DPR₂ is greater than two, more preferablygreater than 5, in some preferred embodiments it is greater than 10, andin some embodiments 5 to 30. The higher the ratio, the less operationalcosts incurred by the manifold from pressure drop it gives.

Decreasing the cross-sectional area of the gates in the direction offlow (see FIG. 3G) in a header manifold improves distribution because(1) a large gate width at the first openings compensates for the largerrelative turning losses seen for the first interface in the manifold;and (2) for gates downstream of the first gate, decreasing the gate sizeand increasing the turning loss penalty can counteract the increase instatic pressure down the length of the manifold, caused by manifoldmomentum compensation.

Flow Regime

The relative momentum of the manifold stream flow plays an importantpart in manifold physics. For M2M manifolds with large head values,momentum compensation and turning losses become more pronounced, and canhave greater influence on fluid flow distribution than manifold frictionlosses. However, if the manifold flow does not have a large head value,the friction losses become the dominant effect and the use of manifoldfeatures that compensate for the high momentum phenomena lose theireffectiveness. As mentioned previously, microchannel M2M manifolds canachieve large head values at low Reynolds numbers because their smallhydraulic diameters compensate for large velocities and mass flux rates.These large head values can occur in laminar flow regimes, well belowthe Reynolds number values of transition and turbulent flow. With largepipe and duct manifolds systems the same head values would be in theturbulent regime due to their inherently larger hydraulic diameters.

The regime of flow entering a macromanifold is typically turbulent ortransition. The flow then undergoes additional regime change in themanifold within the microdevice from turbulent, to transition, tolaminar. Alternatively, the flow may only undergo one regime change,from turbulent to transition or from transition to laminar.

As a means of determining if a M2M manifold has a large head value, wecan use the ratio Mo:

$\begin{matrix}{{Mo} = {\frac{\frac{1}{2\rho}\left\lbrack {G^{2} - 0} \right\rbrack}{\frac{4{fL}_{M\; 2M}}{D}\frac{G^{2}}{2\rho}} = \left\{ \frac{4{fL}_{M\; 2M}}{D} \right\}^{- 1}}} & (1)\end{matrix}$

whereD [m]=manifold hydraulic diameter at the M2Mf [dimensionless]=Fanning friction factor for the M2M. The source ofFanning friction factors for channels is given in Rohsenow et al[“Handbook of Heat Transfer”, 3^(rd) ed. McGraw Hill, 1998] for a widerange of channel geometries, along with references. Care should beplaced in using appropriate Reynolds numbers, channel geometry factors(such as aspect ratios), and hydrodynamic dimensionless lengths(x⁺=LM2M/D/Re for laminar flows) for the Fanning friction factor.G [kg/m²/s]=mass flux rate at the M2MRe [dimensionless]=Reynolds number at the M2MThe ratio Mo (see equation 18) compares the largest M2M manifold headvalue, the driving force for turning losses and momentum compensationstatic pressure changes, to the friction losses the manifold would seeif the largest M2M manifold head was applied over the entire manifoldlength LM2M. Small values of Mo would indicate that the M2M effectswould be small in comparison to the friction losses, negating some ofthe effectiveness of sub-manifolds and all the effectiveness of gratesand gates to control flow distribution. If the Mo value was greater thansome small ratio, for example, Mo>0.05, the head driven turning lossesand momentum compensation terms contribute to flow distribution. Forcases when Mo is greater than 0.05 sub-manifolds, grates, gates andother architecture that manipulate the turning losses and manifoldstatic pressure profiles can improve M2M manifold flow distribution. Forcases when Mo is less than 0.05, manifold friction losses dominate flowdistribution.

An alternate for the Mo number is the FA number. The purpose of FAnumber is to avoid the laminar creeping flow distributed over shortmanifold lengths. The FA expression is a function of flow rate/flowregime (or Reynolds number), hydraulic diameter of manifold and Lengthof manifold. Below is the expression of FA number:

${FA} = {\frac{\left\lbrack {0.058 + {0.0023\left( {\ln \mspace{11mu} {Re}} \right)^{2}}} \right\rbrack^{2}D}{L_{M\; 2M}} < 0.01}$

where hydraulic diameter D in inches, manifold length LM2M in inches andReynolds number Re have the same definition as that for Mo.

In preferred embodiments, FA<0.01. For example, if the hydraulicdiameter of sub-manifold is 0.080″ (0.20 cm), then the table below givesthe length requirement of a sub-manifold with FA<0.01.

Reynolds Length of sub- number manifold (in) 10 L_(M2M) >0.04″ 100L_(M2M) >0.09″ 1000 L_(M2M) >0.23″ 10000 L_(M2M) >0.51″ 100000L_(M2M) >1.05″ This means for Re = 10 and D = 0.08″(0.20 cm), anymanifold design with sub-manifold length >0.04″ (0.10 cm) will have FA<0.01.

Construction of a 5 Stream, Integrated Combustor and Reformer

A microchannel-based module was designed to perform steam-reforming ofmethane, with heat supplied by combustion of air and fuel. Thecombustion and steam reforming reactions are conducted in the samedevice, which has three zones:

Manifold: The manifold zone distributes flow into the channels. Thereare five streams that need to be manifolded. These streams are—Fuel,Air, Exhaust, Reactant and Product. Fuel and air comes into the deviceand leaves out as exhaust. The reactant comes in, gets processed andexits as Products.

Heat exchanger: The exhaust and the products leaving the device are athigh temperature. The heat exchanger recuperates the heat from exhaustand product streams to fuel, air and reactant streams. This recuperationhelps in achieving the necessary temperature of streams for chemicalreactions in the reactor.

Reactor: The reactor zone is actually a reactor plus a heat exchanger.Most of the chemical reactions occur in the reactor zone. The reactionsoccurring in the device are: combustion in the fuel channel (bothcatalytic and homogeneous), and catalytic steam methane reformingreaction in reactant channel. In an optional embodiment, somepre-reforming of either the fuel or process feed may occur in acatalytically coated heat exchanger section.

The fuel channel is coated with different types of catalyst whichpromotes combustion at low temperatures (heterogeneous combustion). Theheat of combustion is transferred through the wall to the reactionchannel. This heat drives the steam-reforming reaction.

A module combustion M2M manifold was designed to achieve equal flowdistribution of combustion reaction streams (fuel such as natural gas,hydrogen, carbon monoxide, and the like with or without air to the fuelside, air to the air side) to the array of combustion channels so thatthey would mix inside the connecting microchannels within the module.The air and fuel enter from opposite sides of the module, mix within thecombustion section, and the combined exhaust makes a u-turn beforetraveling down the return microchannel and leaves the end of the module,forming header L-manifolds for both streams.

Since each M2M manifold feeds multiple separate millisecond contact timemicrochannel reactors (72 in this example, but could range from severalto tens of hundreds), it has to distribute large flow rates that havehigh dynamic pressure (G²/(2ρ)=ρU²/2) values. The total combined M2M andchannel pressure drop was important, and achieving a good distributionof air and fuel in each channel was especially important due to the needto mix near stoichiometric mixtures of fuel and oxidant (air). The meansof achieving equal flow distribution for this system was complicated bya number of fabrication and macro manifold constraints. The resultingdesign included innovations such as: multiple (six, in the illustratedexample) sub-manifolds with multiple (12) channels per sub-manifold; andmultiple (3) gates per sub-manifold with multiple (4) downstreamconnecting channels per gate.

FIG. 4A is an exploded view of shims in the stacked device. FIGS. 4-22are overhead views of shims that were assembled into the device. Theoverall size of all the shims is 31.47″ (length)×22.00″ (width). Theshim length and width are as defined in FIG. 4B1. The thickness of theshim is defined in the direction perpendicular to length and width.Shims from 1-28 were stacked on top of each other to form a repeatingunit of the device. The stack height of the repeating unit is 0.43″.There are total 49 repeating units in the device. The overall height ofthe device is 23.1″. For all the shims, a perimeter margin of 1.00″along the length and 1.50″ along the width has been marked. This markedperimeter metal does not become the part of final device and wasprovided only to enhance metal diffusion bonding. Toward the bottom andsides of all the shims, rectangular slots are made. The purpose of theseslots is to provide a location indicator for opening sub-manifoldsduring post-bonding fabrication operations, such as plungeelectrodischarge machining. The slots on the right side are for fuelstream 12 and reactant stream 14 sub-manifolds, the slots on the leftside are for air stream 16 and product stream 18 and the slots at thebottom 19 are for exhaust stream.

All the openings in the shims are through slots or holes. Passages forthe flow in the device are through slots or holes. The flow between thepassages is separated either by ribs (within a shim for the same stream)or wall shims (between different streams)

FIG. 4B1 shows a wall shim. The thickness of the shim is 0.020″. Thisshim separates the reforming reaction stream from the fuel stream. Theshim also transfers heat generated in combustion channels to thereaction channels for the steam reforming reaction.

FIG. 51 shows a wall shim. The thickness of the shim is 0.020″. Thisshim separates the reactant stream from fuel stream. The shim alsotransfers heat generated in combustion channels to the reactant channelsfor steam reforming reaction. The slots 32 in the shims are to holdcatalyst support fins in the fuel channel.

FIG. 61 shows a shim that forms the passage for fuel stream. Thethickness of the shim is 0.012″. The slots on the shims form featuresfor the fuel stream. The fuel enters from the right end of the shimthrough 6 inlets 44 (referred as sub-manifolds). The widths of thesesub-manifolds perpendicular to the direction of flow, starting from thebottom are 0.60″, 0.60″, 0.55″, 0.50″, 0.50″ and 0.40″. All sixsub-manifolds are separated by 0.060″ rib. The lengths of thesub-manifolds in the flow direction, starting from the bottom are16.93″, 14.11″, 11.29″, 8.47″, 5.65″, and 2.83″. The flow from eachsub-manifold distributed into three super-channels as shown in thedrawing. The flow goes over a 0.060″ rib to enter the super-channel fromsub-manifolds. The length of super-channels in the direction of flow is0.50″. Each super-channel further divides the flow into four channels.the numerous thin channels 42 are separated by 0.060″ ribs except forevery 4th rib which is 0.120″. All the channels 42 are 0.160″ wide. Theflow passes through the heat exchanger zone 46, receiving heat fromexhaust and product stream and enters combustion zone 48. In thecombustion zone, fuel mixes with air and combusts in the presence ofcombustion catalyst.

FIG. 71 shows another shim that forms the passage for fuel stream inconjunction with the shim shown in FIG. 61. The thickness of this shimis 0.025″. The slots on the shims form features for fuel stream. Thefuel enters from the right end of the shim through 6 inlets 52 (referredas sub-manifolds). The widths of these sub-manifolds perpendicular tothe direction of flow, starting from the bottom are 0.60″, 0.60″, 0.55″,0.50″, 0.50″ and 0.40″. All six sub-manifolds are separated by 0.060″ribs 54. The lengths of the sub-manifolds in the flow direction,starting from the bottom are 16.93″, 14.11″, 11.29″, 8.47″, 5.65″, and2.83″. The sub-manifolds have small openings 56 (gates) to meter theflow into the channels. Each sub-manifold has 3 gates. There are a totalof 18 gates to meter the flow into the channels. The length of the gatesin the flow direction is 0.060″. The widths of the gates starting fromthe right are—0.105″, 0.102″, 0.094″, 0.122″, 0.199″, 0.103″, 0.143″,0.142″, 0.127″, 0.160″, 0.161″, 0.145″, 0.299″, 0.230″, 0.152″, 0.560″,0.555″, and 0.550″. The channels 58 are separated by 0.060″ ribs exceptfor every 4th rib which is 0.120″. All the channels are 0.160″ wide. Theflow passes through the heat exchanger zone 57, receiving heat fromexhaust and product stream and enters combustion zone 59. In thecombustion zone, fuel mixes with air and combusts in the presence ofcombustion catalyst.

FIG. 81 illustrates a jet shim that acts as a wall shim between fuel andair stream in the manifold and heat exchanger zone. The thickness ofthis shim is 0.010″. In the combustion zone, this shim provides passages62 (referred as orifices) to mix air into fuel. For every channel (fuelor air), there are 18 orifices to mix air into fuel. Beginning from thebottom, the first orifice is rectangular slots with semi-circular endsof diameter 0.012″. The longest length of the slot is in the directionof flow. The second orifice is equilateral triangular in shape with0.012″ side length and is placed at a distance of 0.133″ from firstorifice. The third & fourth orifices are of 0.012″ diameter holes placed0.267″ from the first orifice. The fifth orifice is again a sametriangular slot placed 0.386″ from the first orifice. Orifice six tofifteen are circular holes with diameter 0.012″ and are placed at0.594″, 0.769″, 0.969″, 1.168″, 1.615″, 2.112″, 2.658″, 3.257″, 3.257″,3.857″, 4.624″ from the first orifice. Orifice sixteen and seventeen are0.012″ diameter holes place 5.392″ from first orifice.

A continuous 0.050″ slot 64 is made on the top of the shim to transportcombusted fuel (exhaust) over to exhaust channel. This slot allows flowto travel between connecting channels in between the header and thefooter.

FIG. 91 shows the shim that forms the passage for the air stream. Thethickness of the shim is 0.012″. The slots on the shims form featuresfor air stream. The air enters from the left end of the shim through 6inlets 92 (referred as sub-manifolds). The widths of these sub-manifoldsperpendicular to the direction of flow, starting from the bottom are0.60″, 0.60″, 0.55″, 0.50″, 0.50″ and 0.40″. All six sub-manifolds areseparated by a 0.060″ rib. The lengths of the sub-manifolds in the flowdirection, starting from the bottom are 16.93″, 14.11″, 11.29″, 8.47″,5.65″, and 2.83″. The flow from each sub-manifold distributes into threesuper-channels 94 as shown in the drawing. The flow goes over 0.060″ rib96 to enter the super-channel from sub-manifolds. The length ofsuper-channels in the direction of flow is 0.50″. Each super-channelfurther divides the flow into four channels. These channels areseparated by 0.060″ ribs except for every 4th rib which is 0.120″. Allthe channels 99 are 0.160″ wide. The flow passes through the heatexchanger zone, receiving heat from exhaust and product stream andenters the combustion zone. In the combustion zone, air flows into theF1 (FIG. 41) and F2 shim (FIG. 51) through orifices 62 to combust thefuel. A continuous 0.050″ tall slot 95 is made on the top of the shim totransport combusted fuel (exhaust) over to the exhaust channel.

FIG. 101 shows another shim that forms the passage for the air stream inconjunction with the shim shown in FIG. 91. The thickness of the shim is0.025″. The slots on the shims form features for the air stream. The airenters from the left end of the shim through 6 inlets (referred assub-manifolds). The widths of these sub-manifolds perpendicular to thedirection of flow, starting from the bottom are 0.60″, 0.60″, 0.55″,0.50″, 0.50″ and 0.40″. All six sub-manifolds are separated by a 0.060″rib. The lengths of the sub-manifolds in the flow direction, startingfrom the bottom are 16.93″, 14.11″, 11.29″, 8.47″, 5.65″, and 2.83″. Thesub-manifolds have small openings (gates) to meter the flow into thechannels. Each sub-manifold has 3 gates 104. There are total 18 gates tometer the flow into the channels. The length of the gates in the flowdirection is 0.060″. The widths of the gates starting from the rightare—0.188″, 0.175″, 0.172″, 0.165″, 0.167″, 0.167″, 0.240″, 0.235″,0.232″, 0.260″, 0.260″, 0.260″, 0.277″, 0.277″, 0.277″, 0.590″, 0.580″,and 0.588″. The channels are separated by 0.060″ ribs except for every4th rib which is 0.120″. All the channels are 0.160″ wide. The flowpasses through the heat exchanger zone, receiving heat from exhaust andproduct stream and enters the combustion zone. In the combustion zone,air flows through the jet shim to react with the fuel in the fuelchannels. A continuous 0.050″ tall slot 106 on the top of the shim totransports combusted fuel (exhaust) over to exhaust channel.

FIG. 111 shows a wall shim that separates the air stream from theexhaust stream. The thickness of the shim is 0.010″. On the top of theshim there are slots through which combusted fuel (exhaust) passes overto the exhaust channel.

FIG. 121 shows a shim with exhaust stream channels. The thickness of theshim is 0.020″. The exhaust stream flows from top of the shim to thebottom of the shim. All the passages for the flow are 0.160″ wide andare separated by 0.060″ ribs except for every 4th rib which is 0.0120″.The exhaust enters a passage from a U-turn at the top of the shim,passes through the heat exchanger zone exchanging heat with fuel and airand flows out at the bottom of the shim.

FIG. 131 shows a shim with exhaust stream channels that pair with thechannels in the shim shown in FIG. 12. The thickness of the shim is0.020″. The exhaust stream flows from top of the shim to the bottom ofthe shim. All the passages for the flow are 0.160″ wide and areseparated by 0.060″ ribs except for every 4th rib which is 0.0120″. Theexhaust enters at the top of the shim in the reactor zone, passesthrough the heat exchanger zone exchanging heat with fuel and air andflow out at the bottom of the shim. At the bottom, a rib 132 of 0.060″serves as support for bonding.

Another shim identical to the shim in FIG. 12 is stacked over the shimin FIG. 13.

Another shim identical to the shim in FIG. 11 is next in the shim stack.Followed by another shim identical to that shown in FIG. 10. Followed byanother shim identical to that shown in FIG. 9. Followed by another shimidentical to that shown in FIG. 8. Followed by another shim identical tothat shown in FIG. 7. Followed by another shim identical to that shownin FIG. 6. Followed by another shim identical to that shown in FIG. 5.Followed by another shim identical to that shown in FIG. 4B.

FIG. 141 shows the shim that forms the passage for reactant stream. Thethickness of the shim is 0.010″. The slots in the shim form passages forthe flow of reactant stream. The reactant enters from the right end ofthe shim through 6 inlets 142 (referred as sub-manifolds). The widths ofthese sub-manifolds perpendicular to the direction of flow are 0.539″.All six sub-manifolds are separated by 0.060″ rib. The lengths of thesub-manifolds in the flow direction, starting from the bottom are16.93″, 14.11″, 11.29″, 8.47″, 5.65″, and 2.83″. The sub-manifolds havesmall openings 144 (gates) to meter the flow into the channels. Eachsub-manifold has 3 gates. There are a total 18 gates to meter the flowinto the channels. The length of the gates in the flow direction is0.060″. The widths of the gates starting from the right are—0.229″,0.209″, 0.173″, 0.229″, 0.209″, 0.173″, 0.229″, 0.209″, 0.173″, 0.229″,0.209″, 0.173″, 0.229″, 0.209″, 0.173″, 0.229″, 0.209″, and 0.173″. Thechannels are separated by 0.060″ ribs except for every 4th rib which is0.120″. All the channels are 0.160″ wide. The length of the flow passagein the shim from the respective sub-manifold is 0.70″. In the reactorzone, slots 146 (7.00″ long and 0.82″wide) are made. The purpose ofthese slots is to hold the fins which provide surface area forsteam-reforming reaction.

FIG. 151 shows another shim that forms the passage for reactant streamin conjunction with the shim shown in FIG. 151. The thickness of theshim is 0.012″. The reactant enters from the right end of the shimthrough 6 inlets 152 (referred as sub-manifolds). The widths of thesesub-manifolds perpendicular to the direction of flow are 0.539″. All sixsub-manifolds are separated by 0.060″ rib. The lengths of thesub-manifolds in the flow direction, starting from the bottom are16.93″, 14.11″, 11.29″, 8.47″, 5.65″, and 2.83″. The flow from eachsub-manifold distributed into three super-channels as shown in thedrawing. The flow goes over a 0.060″ rib 154 to enter the super-channel156 from sub-manifolds. The length of super-channels in the direction offlow is 0.539″. Each super-channel further divides the flow into fourchannels 158. Channels are separated by 0.060″ ribs except for every 4thrib which is 0.120″. All the channels are 0.160″ wide. The flow passesthrough the heat exchanger zone, receiving heat from product and exhauststream and enters the reactor zone. In the reactor zone, the steamreforming reaction occurs in the presence of combustion heat.

FIG. 161 shows a wall shim that separates the reactant stream from theproduct stream. The thickness of the shim is 0.010″. A continuous 0.050″slot 162 is made on the top of the shim to transport products formed inthe reactant channel over to the product channel.

FIG. 171 shows the wall shim and separates the reactant stream from theproduct stream. The thickness of the shim is 0.010″. A continuous 0.21″tall slot 172 is made on the top of the shim serves to transportproducts formed in the reactant channel over to the product channel.

FIG. 181 shows a shim for product flow. The thickness of the shim is0.018″. The product flows in the passages from the top of the shim tothe bottom of the shim. Passages are 0.160″ wide and are separated by0.060″ rib except for every 4^(th) rib which is 0.120″ wide. The flowfrom the passages is then collected in another set of passages 184(referred as sub-manifold) that run perpendicular to first set ofpassages. These passages are separated from first set of passages by0.060″ ribs that in conjunction with shims in FIG. 171 and FIG. 191 form“grates”. The width of each sub-manifold in the direction perpendicularto flow direction is 0.539″. The lengths of sub-manifolds in the flowdirection starting from bottom sub-manifold are 16.93″, 14.11″, 11.29″,8.47″, 5.65″, and 2.83″.

FIG. 191 shows a wall shim that separates reactant stream from productstream. The thickness of the shim is 0.010″. A continuous 0.21″ tallslot 192 is made on the top of the shim to transport products formed inthe reactant channel over to the product channel.

FIG. 201 shows a wall shim and separates reactant stream from productstream. The thickness of the shim is 0.010″. A continuous 0.050″ tallslot 202 is made on the top of the shim to transport products formed inthe reactant channel over to the product channel.

FIG. 211 shows the shim that forms the passage for reactant stream. Thethickness of the shim is 0.012″. The reactant enters from the right endof the shim through 6 inlets 212 (referred as sub-manifolds). The widthsof these sub-manifolds perpendicular to the direction of flow are0.539″. All six sub-manifolds are separated by 0.060″ ribs 214. Thelengths of the sub-manifolds in the flow direction, starting from thebottom are 16.93″, 14.11″, 11.29″, 8.47″, 5.65″, and 2.83″. The flowfrom each sub-manifold distributed into three super-channels 216 asshown in the drawing. The flow goes over a 0.060″ rib 218 to enter thesuper-channel from sub-manifolds. The length of super-channels in thedirection of flow is 0.539″. Each super-channel further divides the flowinto four channels 219. Channels are separated by 0.060″ ribs except forevery 4th rib which is 0.120″. All the channels are 0.160″ wide. Theflow passes through the heat exchanger zone, receiving heat from productand exhaust stream and enters the reactor zone. In the reactor zone, thesteam reforming reaction occurs in the presence of combustion heat.

FIG. 221 shows a drawing of a shim that in conjunction with shim in FIG.211 forms the flow channels for reactant stream. The slots in the shimform passages for the flow of reactant stream. The reactant enters fromthe right end of the shim through 6 inlets (referred as sub-manifolds).The widths of these sub-manifolds perpendicular to the direction of floware 0.539″. All six sub-manifolds are separated by 0.060″ rib. Thelengths of the sub-manifolds in the flow direction, starting from thebottom are 16.93″, 14.11″, 11.29″, 8.47″, 5.65″, and 2.83″. Thesub-manifolds have small openings (referred as orifices) to meter theflow into the channels. Each sub-manifold has 3 orifices. There aretotal 18 orifices to meter the flow into the channels. The length of theflow opening in the flow direction is 0.060″. The widths of the openingsstarting from the right are—0.229″, 0.209″, 0.173″, 0.229″, 0.209″,0.173″, 0.229″, 0.209″, 0.173″, 0.229″, 0.209″, 0.173″, 0.229″, 0.209″,0.173″, 0.229″, 0.209″, and 0.173″. The channels are separated by 0.060″ribs except for every 4th rib which is 0.120″. All the channels are0.160″ wide. The length of the flow passage in the shim from therespective sub-manifold is 0.70″. In the reactor zone, slots (7.00″ longand 0.82″wide) are made. The purpose of these slots is to hold the finswhich provide surface area for steam-reforming reaction.

Manifolding and Microchannel Features

Cross-sectional area restrictions in gates and grates, preferably at thefront of connecting channels, can be formed, for example, by: holesthrough walls, bumps from a lower surface, wall projections, andcombinations of these. Features such as rounded bumps can be formed byetching.

Manifold walls can be rounded (such as to appear like a race track).Flow into a manifold can enter from above or below; and, in manypreferred embodiments, in-plane, such as from a side header attached tothe side of a laminated shim stack. Manifold walls can be solid or withgaps.

In some embodiments (see FIG. 23), a manifold (in the illustrated case,a footer) can be used to separate two phases of differing density in amicrochannel device by gravity and/or centrifugal forces.

Walls between connecting channels may be the same or different lengths.Gates to groups of channels can be centered or offset from the center ofthe gate's connecting channels. FIG. 24 illustrates a manifold structurewith an offset gate and channels of differing lengths. In theillustrated manifold, flow momentum (of a stream entering from the sideof the connecting channels) for a centered gate would tend to force thegreatest flow through downstream channel 242 on the far right side dueto the incoming stream coming from left to right; however, the gate 244positioned in the downstream portion of the manifold (in the illustratedembodiment, the gate is attached to the downstream manifold wall 246)blocks a portion of the flow. Another feature that can be usedindependently of or in conjunction with offset gates are longer internalwalls 248 (not 246) positioned downstream (relative to the direction offlow into the manifold) to restrict flow. Thus, flow is more equallydistributed through the connecting channels. In preferred embodiments,at least one internal channel wall in the downstream section 249 of aconnecting channel set is longer than a channel wall in the upstreamsection. More preferably, at least two (or at least 4) internal channelwalls in the downstream section 249 of a connecting channel set arelonger than a channel wall in the upstream section. Still morepreferably, the downstream section 249 of a connecting channel setcontains at least two internal channel walls 243, 248 that projectprogressively further into a manifold zone 245. Preferably, there are acombination of an offset and at least one internal channel wall in thedownstream section 249 of a connecting channel set longer than a channelwall in the upstream section, since this combination can provide moreequal flow distribution (smaller Q₁ or Q₂) for large flow rates thaneither feature individually. In this embodiment, “longer” meansprojecting the channel further into a manifold zone 245. A similardesign concept can also be used for the footer. When the steams of twoor more connecting channel combine at a manifold connection, the streamfrom the connecting channel farthest from the footer manifold's outletwill have a larger momentum vector in the manifold's flow direction thanthose connecting channel closer to the manifold's exit. This will lowerthe flow resistance for the farthest away channel for leaving themanifold connection, so to balance the flow leaving the channels we canthen vary the geometry around the channel as described above for 242.

FIG. 25 a illustrates flow straightening in a multiple gateconfiguration. Flow enters from the side and is momentum biased towardflow through the downstream portion of the connecting channels. Gates256, 258 can be used to equalize flow between channel sets 257, 259.Flow through connecting channels 254 can be equalized by extending thelength of a manifold zone a distance L₂ (or, in the case of FIG. 25 a, asubmanifold zone 252). Preferably, the zone has a length L₂ of at leastthree times longer than the manifold length L_(M2M) (see FIG. 1A1) inthe flow direction, in some embodiments at least 6 times longer than themanifold length L_(M2M), in some embodiments, to save space L₂ is 20times or less longer than the manifold length L_(M2M). Unless correctedby other means, shorter zones suffer from biased flow while excessivelylong zones may unnecessarily add cost and reduce performance (forexample, by adding frictional losses). Like all features describedherein, this feature can be combined with the other designs describedherein.

FIG. 25 b 1 shows a manifold with a straightening zone 2502 and a flowbump (a grate) 2504 before the entrance of the connecting channels 2506.Entering stream 2505 may come from a side manifold in which flowemanates from above, below, or in the plane. FIG. 25 c is an explodedview of sheets that can be used to form the manifold/channel structure.

FIGS. 26 a and 26 b illustrate a manifold 262 with straight connectingchannels 264. The connecting channels are partially blocked by flowbumps 266. The flow enters the connecting channels from the manifold,but can redistribute amongst channels through the cross-connectingchannels underneath the connecting channels. Two such cross-connectingchannels are shown in FIG. 25 a 1, made by the layer 266. The advantagefor such a system is that cross-connecting channels in 266 can allow forredistribution of flow should manifold design not allow for acceptabledistribution due to space constraints.

A modified version of the structure of FIG. 26 could be microchannelapparatus, comprising: an array of parallel microchannels disposed in aplane;

wherein the array of parallel microchannels are connected at one end byan inlet manifold and at their opposite end by an outlet manifold; andat least one channel disposed above or below the array of parallelmicrochannels and disposed at an angle of at least 20 degrees(preferably substantially 90 degrees) relative to the parallelmicrochannels and disposed between the inlet manifold and outletmanifold and connected via openings to the parallel microchannels in thearray. Such a structure could be obtained by forming connections throughthe walls 265, 267 of second channel 261. The connections through thewalls 265, 267 would connect to an inlet and outlet respectively so thatthere could be cross flow through the second channel. In someembodiments (not shown) a plate can separate the first and second layersexcept for an aperture or apertures through the plate to providecommunication between the first layer and the second channel. Such aconstruction could be used, for example, to mix components or as apathway to add a coating material from one layer to the next.

FIG. 27 is an exploded view (also a preassembled view) of an alternativedesign having flow bumps 272, 274 in an alternating arrangement suchthat there is no straight flow path through the connecting channels.This structure creates extensive interchannel mixing.

In addition to flow distribution, manifolds may also perform a mixingfunction. FIG. 28 illustrates a manifold with cross-current flows 282,284 that mix over the length of the manifold zone 286 via gaps 285 individing wall 287. This cross-flow mixing reduces momentum biased flowinto the connecting channels. The mixing can be a single component, twoor more reactants, or two phases. In the illustrated embodiment, thein-flows are coplanar; however, it should be appreciated that mixingcould alternatively or additionally be accomplished through holes in thesheet above or below the manifold.

As illustrated in FIG. 29, a manifold can be inclined to change thecross-sectional area of the manifold in the direction of flow, whichchanges the local connecting channel interface to manifold area ratioand the channel M2M manifold aspect ratio. By “inclined” is meant thatthe height (not merely the width) of the manifold varies. Preferably,the manifold slopes upward so that the smallest volume is adjacent tothe connecting channel furthest downstream (i.e., the opposite of theslope in FIG. 29). This structure can be made by etching.

In some embodiments, the gates from the manifold to the connectingchannels can be angled. This is schematically illustrated in FIG. 30. Anangled opening can be made by etching. The angled flows can add orsubtract from turning loss resistance and can be designed to make flowmore equal through the connecting channels. Here, “angled” means thatthe gate is sloped such that the center line through the gate forms anangle between 2 and 98 degrees or between 92 and 178 degrees, morepreferably between 20 and 80 or between 100 and 170 degrees with respectto the center line through the connecting channels. Preferably, thedesign is as illustrated where at least one channel (or preferably more)that is in the upstream section of the manifold is angled to reduceturning loss (with flow) while at least one channel (or preferably more)that is in the downstream section of the manifold is angled to increaseturning loss (against flow).

FIG. 31 illustrates an exploded (or preassembly) view of stackedconnecting channels that include an offset region 312 that allowsinterchannel mixing. In an offset configuration, a channel wall or wallsin a first layer extend to provide a fluid pathway into a secondadjacent layer.

Another option to reduce the effects of flow momentum is to placebaffles within the headers (not shown).

FIG. 32 illustrates an alternative form of gate in which porous bodiesare placed between a manifold 322 and connecting channels. Preferablyfor a header manifold for a Z-manifold or L-manifold the porous bodiesare arranged such that the greatest resistance to flow is present in theporous body 324 furthest downstream relative to the manifold while therelatively less resistance to flow is present in upstream porous body326 for a header manifold with a Mo value greater than 0.05. This putsthe highest flow resistance for the zone with the highest staticpressure value in the manifold, a product of increasing static pressurefrom momentum compensation. A header for a U-manifold with a Mo valuegreater than 0.05 may want the order reversed from that described forthe Z-manifold and L-manifold headers to compensate for momentumcompensation and friction losses in the footer. More generally, it ispreferred that a porous body with a relatively greater resistance toflow is located downstream in the header manifold relative to a porousbody with a relatively lesser resistance to flow for a header manifoldfor a Z-manifold or L-manifold. The reverse is true for the U-manifold.For flow distribution through connecting channels of equal width, atleast 3 porous bodies increase in flow resistance with increasingdistance downstream in the manifold. The porous bodies can be catalytic(e.g. in a reactor) or noncatalytic. A foam is a preferred example of aporous body.

FIG. 33 illustrates an embodiment in which flow is affected by aflexible projection 332 through a channel wall. The flexible projectioncan project from one side of a wall or through a channel wall and intoboth adjacent channels.

Multiple microdevices 3402, 3404, each with an internal micro-to-macromanifold may be further connected together with a macromanifold 3405(see FIG. 34A) to achieve any desired capacity or productivity. Thislevel of manifolding may comprise pipes or ducts that connect streamsbetween microdevices. At least one stream can be in a single pipe 3406or duct with an inlet 3407 or outlet 3408 to each parallel microdevice.In some embodiments, all streams are connected with a unique pipe orduct. In one embodiment, one or more outlet streams 3409 vents to theatmosphere, such as the case of a combustion exhaust stream.

The pipes or ducts that connect multiple microdevices preferablymaintain a hermetic seal around the respective inlet or outlet of afluid stream for each microdevice. The hermetic seal may be achieved bywelding or gasket connections. For a microdevice with multiple inlets oroutlets, the connecting macromanifold pipes or ducts may be connected toeach other but in a gas-tight manner to prevent cross-stream leaks orconnections. As an example, an inner pipe that contains the inlet forone stream, may contain an outer pipe that is attached to the inner pipearound a portion of the circumference of the inner pipe (not shown).Multiple pipes or ducts may be connected in this manner. An advantage ofthis approach includes a reduced amount of metal weight for themacromanifold, control of the thermal profile along the pipes to reducestress imposed material thickness limits, and reduced total volumerequired for the macromanifold system.

The macromanifold represents the first level of flow distribution. Flowenters from a single source and is distributed to two or moremicrodevices. After flow enters each microdevice it is furtheroptionally segregated into multiple submanifolds. From each submanifold,flow may be further distributed to multiple connecting channels.Finally, an optional embodiment includes a further level of flowdistribution to multiple subchannels within each microchannel. Eachsubchannel may take the form of a fin (either inserted or formedintegrally to the device) or other flow distributor housed within amicrochannel. There may be three, four, or more levels of flowdistribution required for the operation of microdevices that produce aquality index factor of less than 30%, or any of the preferred Q valuesdiscussed herein.

Flow Distribution in Two Dimensions

Where there is a need to distribute flow to two-dimensional array ofconnecting channels, in the stacking direction and in the planes ofchannels, often there are options that allow for using a single manifoldfor distribution. These single manifolds can be large ducts or pipes,and they are often used for cross-flow applications. For these cases,the frictional losses play a smaller role as the length of the manifoldover hydraulic diameter becomes small (L/D ˜1). However, the momentumdriven phenomena, the momentum compensation and turning losses, becomethe main driving force for flow distribution and should be accounted forwithin the design. The manifold physics change from those of the highM2M manifold aspect ratio channel terms discussed in the one dimensionalmanifold section. The less significant turning losses for the highaspect ratio channel is due to the cross-sections of large ducts thathave square perimeters or have pipe or half-pipe perimeters. The turninglosses for these cases have less wall shear stress than seen for thehigh aspect ratio rectangular channels. The next two concepts describemeans of improving flow distribution to two dimensional channel arrays.

One problem with flow distribution is maldistribution through aconnecting channel matrix due to the momentum of incoming flow. Acentral feed inlet and central feed outlet can lead to channelingthrough the center of the matrix, as seen in cross-flow heat exchangers.See Lalot et al, Applied Thermal Engineering, v. 19, pp. 847-863, 1999;Ranganayakulu and Seetharamu, Heat and Mass Transfer, v. 36, pp.247-256, 2000).

Also, a single inlet tangent to the direction of flow can result in astream that distributes the bulk of the flow to the channels opposite tothe inlet and could induce large recirculation zones in the header andfooter, recirculation from the header to the footer and recirculation orstagnant zones in the device.

A device that ameliorates these problems is illustrated in FIG. 34Bwhich is a top-down view inside a channel in a device having multipleinlets 3406 parallel to the direction of flow. In the illustrateddesign, inlet flow is introduced from both sides of a sub-manifold 3402.If flow is introduced from only one side, the bulk of the flow wouldleave via the header inlet farthest from the main inlet. A simulationindicated that that this arrangement was successful in eliminatingrecirculation zones, recirculation from the footer to header andstagnant areas in the device. The basic distribution for this option isbiased to the center but to a greatly reduced extent as compared toother options.

Also illustrated in FIG. 34B are optional flow directors 3404 that candirect flow through a chamber. These flow directors can be louvers (orpaddles) that can be collectively or individually rotated to direct flowin a desired direction. A louver system was designed where all of thelouvers are attached together by an adjoining rod, which will allow allof the louvers to move and rotate at the same time, same direction andto the same position. The use of louvers provides a convenient way ofchanging flow directions within a device. The louvers are able to shiftthe flow such that it can be biased to the left, middle and right. Thus,in one example, the flow directors are rotatable louvers.

In some preferred embodiments, a heat exchange fluid is passed throughthe chamber with the heat exchange fluid biased. Stacked adjacent to theillustrated heat exchange chamber, either above and/or below, is areaction chamber (not shown) in which reactants pass in a cross-flowrelationship relative to the heat exchange fluid. This orientation isadvantageous if the reaction rate is greatest at the front or back ofthe reaction chamber and this high-reacting-rate portion is matched tothe biased flow through the heat exchanger such that the highest flow ofheat exchange fluid is directly adjacent to the highest reaction rate inthe adjacent reaction chamber.

Flow Distribution Plates

In some multichannel design embodiments, at low flow rates, frictionlosses may dominate causing flow to primarily pass through the center ofa multichannel array. One solution to this problem is to place a flowdistribution plate prior to a multichannel array. This concept isillustrated in FIG. 35 which shows flow being forced to the periphery ofa distribution plate 3502. Generally, this can be accomplished by aplate with orifices preferentially distributed nearer the periphery ofthe plate than to the center. Preferably, a second orifice plate 3504with a two-dimensional array of equally distributed holes follows thefirst plate. The combination of the first and second plates, preferablyin further combination with an open redistribution zone (not shown)following the first plate, equalizes pressure over the front surface ofan array and reduces flow maldistribution through a multichannel array.A partially exploded view of a multichannel device using the combinationof first and second flow redistribution plates 3602, 3604 is shown inFIG. 36.

Cross sectional and side views of another design with first and secondflow distribution plates is illustrated in FIG. 37. In this design, thefirst orifice plate 3702 has differing gate sizes to control flow. Thevarying gate sizes can either be used to equalize flow, or to provide anonuniform flow for instances in which nonuniform flow is desired. Inthe cases when local flow maldistribution (within the segment) wouldoccur using one orifice plate, for example, if the frictional loss istoo small in the microchannels (too short of a channel) or velocity inthe orifice is very high, a second orifice plate 3704 with a number oflarge orifices offset from the orifice position of the first plate(i.e., nonaligned) is needed to divert the flow stream from the singleorifice and ensure a uniform distribution within the segment ofmicrochannels (i.e., connecting channel matrix 3706). In someembodiments, because of the difference in turning losses, equal flow canbe obtained with a portion 2710 of the connecting channel matrix indirect contact with the manifold 3708 without intervening orificeplates.

In some embodiments, plates containing one or more orifice are disposedwithin the header. See FIG. 38. In the illustrated device, plates 3802with one or more orifices are of a shape that fits in the header crosssection and can be mounted (sealed or welded) inside the header so as toseparate the header of a microchannel device into several segments. Theorifice sizes are designed according to the desired flow rate andpressure drop for the corresponding group (arrays) of the microchannelsto realize a designed stepwise profile of flow rate and pressure dropover the whole device. As the pressure varies from segment to segment,the segment-averaged flow rate in the microchannels can be differentfrom segment to segment or can also be the same for a uniform flowdistribution. The illustrated design contains 6 microchannels withineach segment; however, it should be realized that any number of channelsmay be present in a segment, for example, in some preferred embodiments,2 to 100 channels, and in some embodiments 10 to 50 channels. Theillustrated design has orifice plates with decreasing orifice sizes inthe direction of flow to compensate for momentum and provide more equalflow through the connecting channels. The illustrated plates areparallel to the connecting channels. By selecting the number of orificeplates, the orifice size or number, the flow rate difference between themicrochannels of a single segment can also be designed and limitedwithin an allowable range. As such, a stepwise flow distribution can beachieved. As one example, if the illustrated layer were a coolant layerin an integrated reactor containing an adjacent reactor layer (notshown) in cross-flow relationship, coolant flow is concentrated in thearea immediately adjacent to the front (hottest part) of the reactorlayer.

Orifice plates can have equally distributed orifices of similar oridentical sizes, monotonically increasing or decreasing open areas, orcan be designed with any desired orifice distribution. For example, FIG.39A shows orifice plates with holes or slots that increase to a maximumarea then decrease down their length. In general, a moveable orificeplate between a manifold and connecting channels can be used to varyflow rate into connecting channels. For example, the plates in FIG. 39Bhave optional screw holes 392 for use as moveable plates. As shown inthe A-A view, the orifice plate can be moved up or down to vary flow.The plate can be mounted and sealed between the header of the device andthe channel inlet face using screws. When a flow distribution profilechange is needed, the relative position between the plate and thechannels can be changed by unscrewing the plate and moving the plate toa position corresponding to the designed new distribution profile. Thus,different flow distribution profiles within the same device can beobtained, and flow rates optimized for varying conditions.

Device Fabrication

Sheets and strips for forming laminated devices can be formed byprocesses including: conventional machining, wire EDM, plunge EDM, lasercutting, molding, coining, water jet, stamping, etching (for example,chemical, photochemical and plasma etch) and combinations thereof. Forlow cost, stamping to cut apertures through a sheet or strip isespecially desirable. Any shaping or forming process can be combinedwith additional steps. Some of the inventive methods can also becharacterized by the absence of certain forming techniques; for example,some preferred methods do not utilize etching, casting, melting apowder, molding, chemical or physical deposition, etc.

To form a laminated device, a sheet or strip is stacked on a substrate.For purposes of the present invention, a substrate is broadly defined toinclude another sheet or strip or a thicker component that could be, forexample, a previously bonded sheet stack. Preferably, multiple sheetsand/or strips are aligned in a stack before bonding. In someembodiments, a brazing compound is placed on one or more surfaces of asheet or strip (or plural sheets and/or strips) to assist bonding.Sheets and strips should be aligned in a stack. Alignment can beachieved by making sheets and/or strips with alignment apertures andthen using alignment pins to align the sheets and/or strips in a stack.A stack (including a subassembly that does not include all thecomponents of a final device) can be lifted from pins, or the pins canbe removed (such as by burning or by pulling out pins), or the pins canbecome bonded in the stack. Another alignment technique utilizes moldsfor aligning sheets and/or strips; this technique can be especiallyuseful for positioning flow modifiers such as ribs. In some embodiments,molds remain in place while the stack components are attached in placesuch as by welding, heating an adhesive, or diffusion bonding;subsequently, the molds are removed. In other embodiments, the mold canbe removed before the components are bonded. Molds can be reusable orcan be single use components that could be removed, for example, byburning out.

The sheets, strips and subassemblies may be joined together by diffusionbonding methods such as ram pressing or hot isostatic pressing (HIPing).They may also be joined together by reactive metal bonding, brazing, orother methods that create a face seal. Welding techniques, such as TIGwelding, laser welding, or resistance welding, may also be used. Devicescan alternatively be joined by the use of adhesives.

In cases where a full length seal is desired to provide fluidcontainment, seam welding can be employed to form a complete sealbetween a substrate, strip and/or flow modifier. Tack or spot weldingcan be used to hold strips, flow modifiers or subassemblies in place,without creating a complete seal along an entire edge. Usually, the tackwelded assemblies will be subjected to a subsequent bonding step.

Brazing techniques and compositions are known and can be employed informing devices of the present invention. Braze cycles longer than about10 hours can result in better devices that show less distortion and havebetter bonding.

Techniques for assembly and/or bonding of devices can use the sametechniques or a mixture of techniques. For example, a subassembly couldbe welded together and then welded to a second subassembly that itselfwas formed by welding. Alternatively, for example, a subassembly couldbe spot welded together, brazed to a second subassembly, and thecombined assembly diffusion bonded.

Numerous microchannel, laminated devices can be made with the componentsdescribed herein and/or structures described herein and/or made usingthe methods described herein. Such laminated devices can be, forexample, heat exchangers, reactors (integrated combustion reactors areone preferred type of reactor), separators, mixers, combinations ofthese, and other microchannel, laminated devices that are capable ofperforming a unit operation. The term “laminated articles” encompasseslaminated devices as well as laminated subassemblies.

While the individual laminae are quite thin, the device dimensions arenot particularly limited because numerous laminae (of a desired lengthand width) may be stacked to any desired height. In some preferredembodiments, the inventive articles contain at least 5 laminae, morepreferably at least 10, and in some embodiments, more than 50. In somepreferred embodiments, the articles contain at least 2, in someembodiments at least 5 repeating units (with each repeating unitcontaining at least 3 different laminae).

In some embodiments, at least one fluid is flowing through the manifold,and in some embodiments, this fluid is a gas. The header or footer canbe shaped to fit an end of a subassembly, for example a square end on aheader/footer to match one side of a cubic subassembly.

The articles may be made of materials such as plastic, metal, ceramic,glass and composites, or combinations, depending on the desiredcharacteristics. In some preferred embodiments, the articles describedherein are constructed from hard materials such as a ceramic, an ironbased alloy such as steel, or monel, or high temperature nickel basedsuperalloys such as Inconel 625, Inconel 617 or Haynes alloy 230. Insome preferred embodiments, the apparatuses are comprised of a materialthat is durable and has good thermal conductivity. In some embodiments,the apparatuses can be constructed from other materials such as plastic,glass and composites. Materials such as brazes, adhesives and catalystsare utilized in some embodiments of the invention.

The present invention may include chemical reactions that are conductedin any of the apparatus or methods of conducting reactions that aredescribed herein. As is known, the small dimensions can result insuperior efficiencies due to short heat and mass transfer distances.Reactions can be uncatalyzed or catalyzed with a homogenous orheterogeneous catalyst. Heterogeneous catalysts can be powders, coatingson chamber walls, or inserts (solid inserts like foils, fins, or porousinserts). Catalysts suitable for catalyzing a selected reaction areknown in the art and catalysts specifically designed for microchannelreactors have been recently developed. In some preferred embodiments ofthe present invention, catalysts can be a porous catalyst. The “porouscatalyst” described herein refers to a porous material having a porevolume of 5 to 98%, more preferably 30 to 95% of the total porousmaterial's volume. The porous material can itself be a catalyst, butmore preferably the porous material comprises a metal, ceramic orcomposite support having a layer or layers of a catalyst material ormaterials deposited thereon. The porosity can be geometrically regularas in a honeycomb or parallel pore structure, or porosity may begeometrically tortuous or random. In some preferred embodiments, thesupport of the porous material is a foam metal, foam ceramic, metal felt(i.e., matted, nonwoven fibers), or metal screen. The porous structurescould be oriented in either a flow-by or flow-through orientation. Thecatalyst could also take the form of a metal gauze that is parallel tothe direction of flow in a flow-by catalyst configuration.

Alternatively, a catalyst support could be formed from a dense metalshim, fin or foil. A porous layer can be coated or grown on the densemetal to provide sufficient active surface sites for reaction. An activecatalyst metal or metal oxide could then be washcoated eithersequentially or concurrently to form the active catalyst structure. Thedense metal foil, fin, or shim would form an insert structure that wouldbe placed inside the reactor either before or after bonding or formingthe microchannel structure. A catalyst can be deposited on the insertafter the catalyst has been inserted. In some embodiments, a catalystcontacts a wall or walls that are adjacent to both endothermic andexothermic reaction chambers.

The invention also includes processes of conducting one or more unitoperations in any of the designs or methods of the invention. Suitableoperating conditions for conducting a unit operation can be identifiedthrough routine experimentation. Reactions of the present inventioninclude: acetylation, addition reactions, alkylation, dealkylation,hydrodealkylation, reductive alkylation, amination, ammoxidationaromatization, arylation, autothermal reforming, carbonylation,decarbonylation, reductive carbonylation, carboxylation, reductivecarboxylation, reductive coupling, condensation, cracking,hydrocracking, cyclization, cyclooligomerization, dehalogenation,dehydrogenation, oxydehydrogenation, dimerization, epoxidation,esterification, exchange, Fischer-Tropsch, halogenation,hydrohalogenation, homologation, hydration, dehydration, hydrogenation,dehydrogenation, hydrocarboxylation, hydroformylation, hydrogenolysis,hydrometallation, hydrosilation, hydrolysis, hydrotreating (includinghydrodesulfurization HDS/HDN), isomerization, methylation,demethylation, metathesis, nitration, oxidation, partial oxidation,polymerization, reduction, reformation, reverse water gas shift,Sabatier, sulfonation, telomerization, transesterification,trimerization, and water gas shift. For each of the reactions listedabove, there are catalysts and conditions known to those skilled in theart; and the present invention includes apparatus and methods utilizingthese catalysts. For example, the invention includes methods ofamination through an amination catalyst and apparatus containing anamination catalyst. The invention can be thusly described for each ofthe reactions listed above, either individually (e.g., hydrogenolysis),or in groups (e.g., hydrohalogenation, hydrometallation andhydrosilation with hydrohalogenation, hydrometallation and hydrosilationcatalyst, respectively). Suitable process conditions for each reaction,utilizing apparatus of the present invention and catalysts that can beidentified through knowledge of the prior art and/or routineexperimentation. To cite one example, the invention provides aFischer-Tropsch reaction using a device (specifically, a reactor) havingone or more of the design features described herein.

EXAMPLE 1 Comparative Calculated Example

Calculations have been conducted based on a design shown in FIGS. 51 to64 of Golbig published patent application US 2002/0106311 A1. In thisdesign, a fluid flows into two separate headers of the same dimensions.The header intersects at a right angle with the ends of connectingchannels of varying widths; the widths varying from widest at the startof the header to the narrowest channel at the end. The object of thisdesign was to enable “viscous fluids to be processed in parallel fluidchannels with substantially equivalent residence time distributions.”The varying channel width tailors the connecting channel flow resistanceto compensate for the differences between the header and footer pressurefor a given fluid viscosity and flow rate, adding resistance to channelswith larger pressure difference driving forces and less resistance tothose with lower pressure difference driving force.

While the publication does not specifically describe all the dimensionsof the design, approximate dimensions can be surmised from the text.From paragraph 292, the shims have a thickness of 0.3 mm, and paragraph295 shows the relative channel widths in units which appear to be amultiplicative factor of channel height. Measuring channel widths fromthe figure, and comparing to the unit dimensions in paragraph 295, wecalculate that 0.1 cm of measured distance is equal to 0.393 mm in thedesign. Similarly, the connecting channel lengths are measured to be13.8 cm, correlating to an actual design length of 54.3 mm, with ribsbetween channels of 0.59 mm, header width of 0.39 mm, and footer widthof 2.55 mm. In paragraph 138 it is stated that limiting openings to amaximum of 2 mm enhances the bonding process—this limit is consistentwith our calculated range of channel openings. The preferred embodimentof this invention is desired to have substantially equivalent residencetimes.

Golbig et al. use an analogy to circuit theory, and use the laminar flowregime to describe flow. Thus, we calculate pressure drop as

$\begin{matrix}\begin{matrix}{{\Delta \; P} = {\frac{4{fL}}{D}\frac{G^{2}}{2\rho}}} \\{= {\frac{4L}{D}\left( \frac{C}{Re} \right)\frac{G^{2}}{2\rho}}} \\{= {\frac{4L}{D}\left( \frac{\mu \; C}{GD} \right)\frac{G^{2}}{2\rho}}} \\{= {{\left( \frac{2\mu \; {CL}}{D^{2}} \right)\frac{G}{\rho}} = {\left( \frac{2\mu \; {CL}}{D^{2}} \right)U}}}\end{matrix} & (1)\end{matrix}$

whereC [dimensionless]=Coefficient, a function of channel dimensions andperimeterf [dimensionless]=C/Re=Fanning friction factorD [m]=Hydraulic diameter=4(cross-sectional area)/(channel perimeter)L [m]=length of channelG [kg/m²/s]=Mass flux rateρ [kg/m³]=DensityRe [dimensionless]=Reynolds number=GD/□U [m/s]=Mean channel velocityμ [kg/m/s]=Dynamic viscosity of the fluidThe resistance for any section becomes

$\begin{matrix}{R = \frac{2\mu \; {CL}}{D^{2}}} & (2)\end{matrix}$

The equation (1.3) assumes fully developed laminar flow, meaning theboundary layer in the channel has fully developed over the channellength L. Using the definition of dimensionless hydrodynamic length x⁺,

$\begin{matrix}{x^{+} = \frac{L}{D\mspace{11mu} {Re}}} & (3)\end{matrix}$

the flow is approaching fully developed flow around a x⁺ value of 0.05,and is much closer to developed flow at a x⁺ value of 1¹. If resistancepath lengths L are small, either the hydraulic diameter D or Re mustbecome small to get reasonable x⁺ values. To meet the limitation ofx⁺>0.05 to 1 for given channel hydraulic diameters, we will look at lowReynolds number values. R. K. Shah and London, A. L. “Advances in HeatTransfer. Supplement 1. Laminar flow forced convection in ducts—A sourcebook for compact heat exchanger analytical data.” Academic Press, NewYork, 1978, p. 212.The system we used for analysis has the same dimensions as describedabove, with the following assumptions and factors:

-   -   Two header inlet mass flow rates of equal flow rate, and the        distributions of the two headers are assumed to be the same.    -   The reactant streams have the mass flux rates from the header,        while the product stream mass flux rate have the combined flow        of the two header inputs for channel i

2G_(react)[i]=G_(prod)[i]  (4)

-   -   Ignore the pressure drop losses in the transitions for the        streams between shims and on mixing, as the first will be a        small addition and the latter because the stream momentums are        so low.    -   Use air at room temperature (20° C.) and have the footer outlet        at 101325 Pascals [Pa] or 1.01325 bar. Golbig's preferred        process doesn't specify a specific temperature rise or species        change, so we are arbitrarily setting the conditions.    -   Quality index factor will be based upon mass flux rates with the        Q₂ equation

$Q_{2} = {\frac{G_{\max} - G_{\min}}{G_{\max}} \times 100\%}$

-   -   The system had two options for the header laminar Fanning        friction factors f,        -   Fully developed flow        -   Developing flow, with the L in the x⁺ equation (0.17) based            on the distance away from the entrance in the header and the            distance from the beginning of the manifold in the footer.            The first case that was investigated was for a flow rate of            10⁻⁰⁶ kg/s flow to each header, with fully developed flow in            the manifolds, and all turning losses and momentum            compensation effects removed. The channel mass flux rates            for the case are plotted in FIG. 401. The Q₂ factor is            almost 71%. The mass flux rate varies from 0.2 to 0.6            kg/m²/s in the channels, with flow favoring the first (i.e.            widest) channels. The header and footer Mo values are on the            order of 0.04 and 0.03, respectively. The pressure drop for            the system was on the order of 350 Pa (3.5×10⁻³ bar) and the            header inlet and footer outlet Reynolds numbers were 159 and            78, respectively. When the momentum compensation, turning            losses and laminar developing flows are added, we get worse            results, as seen in FIG. 411.

As mentioned in the published application, the system dimensions are afunction of the viscosities of the reactants and the products of thereaction system. The case with water at the same mass flow rate was runand the results in FIG. 421 show the results are just as poor.

Doing some optimization of header and footer widths, the Q factor comesdown to 7% by setting the header and footer manifold widths to 0.004 mmand 0.003 mm, respectively. The results are shown in FIG. 431. The Movalues for the header and footer are low, on the order of 0.01. When theflow rates for this case are increased 10 fold to 10⁻⁰⁵ kg/sec perheader manifold, the performance drops precipitously in Q factor, asseen in FIG. 441. The Q factor increases to 33%, and the results showtypical Z-manifold behavior for high momentum flows: higher flux rate atthe last connecting channel in the header compared to the first channel.Note that the header and footer Mo values are higher than 0.05, despitelow Reynolds numbers. Thus, turbulent Reynolds numbers are not requiredto have a high Mo value—high Mo can occur in low laminar flow.

The methodology in Golbig's patent application doesn't show equal flowdistribution (low Q) for fully developed laminar flow at low headvalues, much less so at higher heads that lead to substantial manifoldturning loss and momentum compensation terms. The reason may be therelationship between channel flow resistance and the degree to which theconnecting channel's aspect ratio leads to that resistance. This isshown in Examples 4 and 5.

EXAMPLE 2

This example describes the predicted performance of the SMR module flowdistribution discussed earlier in the application.

In this design, the gate widths grow wider as the length of asub-manifold's upstream length increases, and the width of asub-manifold increases as the sub-manifold's upstream length increases.By using the widths of both sub-manifolds and gates withinsub-manifolds, the overall pressure drop seen in each sub-manifold wasequalized in both air and fuel header M2M manifolds. The sub-manifoldwith the shortest path length (#1) across the shim has the thinnestsub-manifold width and the thinnest gates, while the sub-manifold withthe longest path across the shim (#6) has the widest sub-manifold widthand widest gates. The relative dimensions for the manifolds are givenbelow in Table 1.

TABLE 1 Dimensions for the combustion M2M air and fuel sub-manifoldslisted per sub-manifold number. Gate number is given in the order thatthe manifold stream sees the gate, i.e. #1 for the first gate seen inthe sub-manifold and #3 for the last gate seen. Sub-manifold M2M channelWidth of air Gates (inches) Width of Fuel Gates (inches) number width(in) #1 #2 #3 #1 #2 #3 1 0.400 0.188 0.175 0.172 0.105 0.102 0.094 20.500 0.165 0.167 0.167 0.122 0.119 0.103 3 0.500 0.240 0.235 0.2320.143 0.142 0.127 4 0.550 0.260 0.260 0.260 0.160 0.161 0.145 5 0.6000.277 0.277 0.277 0.299 0.230 0.152 6 0.600 0.590 0.580 0.588 0.5600.555 0.550

As fluid leaves the sub-manifold's distribution zone into the gates, theconstant width of the section leads to a static pressure increase tocompensate the loss of dynamic pressure, minus whatever frictionallosses occur in that zone. With each gate, the static pressure has thepotential to increase or stay steady in this high momentum (dynamicpressure) flow, but the turning losses aren't constant over themanifold. The use of gate widths, such as in Table 1, allow us to tailorthe local pressures in the device for better flow distribution. Ingeneral, decreasing the gate width with increasing gate number in asub-manifold overcomes the momentum compensation factors in the header.FIGS. 451 and 461 show the model results for the header and gate staticpressures plotted versus the gate number (18 total per manifold) for airand fuel respectively. The lower number gates add additional backpressure to compensate for shorter upstream manifold lengths. The use ofthe gates achieves an even pressure at the gates across the module,equalizing the pressure drop driving force to the exhaust outlet at 0.25psig. The DPR3 ratios for both fuel and air manifolds are high for gatesone through three in the first sub-manifold, but the average value isabout 0.5 because the turning losses decrease as the sub-manifold numberincreases.

Results of the coupled combustion manifold are seen in FIG. 471, showingthe model predictions of the 72 channel flow rates for air and fuelplotted versus the fuel channel number. The overall results are listedbelow.

Total air M2M mass flow rate: 14.96 kilograms per hourTotal fuel M2M mass flow rate: 4.84 kilograms per hour (Natural gas andair)Total air M2M quality index factor: 3.9%Total fuel M2M quality index factor: 6.1%Air M2M sub-manifold to sub-manifold quality index factor: 0.2%Fuel M2M sub-manifold to sub-manifold quality index factor: 0.5%Inlet air M2M pressure (including turning loss from macro manifold):8.16 psigInlet fuel M2M pressure (including turning loss from macro manifold):6.61 psig

EXAMPLE 3

This example is a calculated example based on a sub-manifold that hasthe following features: L-manifold header, like that described; constantwidth, height of M2M manifold; 3 “gates”, each serving four connectingchannels downstream of the distribution section; and high momentum flow(Entrance Mo=0.7>>0.05). The conditions are: an outlet pressure of 1 atm(101325 Pa); air flow of 38.22 SLPM; and 20° C.

The header M2M manifold dimensions are:

-   -   0.041″ height, made from a 0.017″ and a 0.023″ shims and a        0.001″ tall gasket    -   0.400″ wide for the entire manifold (W_(m))    -   A_(M)=1.04×10⁻⁵ m²    -   Lengths:        -   From macro manifold connection to first gate: 1.250″            (=L_(u,1))        -   From macro manifold connection to end of the manifold 3.700″        -   Lengths for friction losses:            -   L_(c,1)=0.270″            -   L_(c,2)=0.250″            -   L_(c,3)=0.245″            -   L_(u,1)=1.250″            -   L_(u,2)=0.680″            -   L_(u,3)=0.692″

Gate and Distribution Section Dimensions:

-   -   Center position of gates from macro manifold:        -   1^(st): 1.410″        -   2^(nd): 2.350″        -   3^(rd): 3.290″    -   Gate channel height: 0.024″    -   Length of gate opening in flow direction: 0.060″    -   Gate widths:        -   1^(st): 0.270″ (A_(c,1)=0.0000041 m²)        -   2^(nd): 0.250″ (A_(c,2)=0.0000039 m²)        -   3^(rd): 0.245″ (A_(c,3)=0.0000038 m²)    -   Dimensions of each gate downstream distribution section:        -   Length: 0.500″        -   Height: 0.040″ total—0.017″ is in the open “picture frame”            shim        -   Width: 0.820″    -   Connection to downstream connecting channels        -   Through the 0.024″ wide channel        -   0.060″ total length to connecting channel

Connecting Channel Dimensions

-   -   Twelve channels, 0.160″ wide    -   Four channels per gate, each separated by 0.060″ wide ribs (3        per gate)    -   Two 0.120″ wide ribs separating the channels (2 total)    -   2.700″ wide connecting channel matrix    -   Heights and widths        -   For 1.000″ downstream of the gate distribution section            -   0.041″ channel height            -   A_(cc)=0.0000042 m²        -   For the last 11.500″ of the channel            -   0.018″ channel height            -   A_(cc)=0.0000018 m²    -   The channel flows end abruptly, exiting out to ambient pressure.

Equations.

Same as described in the Discussion section, but with the followingadditions to the downstream resistance. The gate distribution sectionhas a resistance term for each of the four downstream channels,dependent upon gate Reynolds number. The gate has a mass flow ratecontinuity equation to distribute the flows. The connecting channelpressure drop has two major resistances: friction losses for the 1.000″long section downstream of the gate; friction losses for the last11.500″ of the channel; and the sudden contraction losses and the exitlosses are ignored.

Results.

FIG. 481 shows the mass flow rates in each connecting channel. Thepredicted quality index factor Q₁ is 2.2%. FIG. 491 shows the predictedpressures in the header and the gates across the manifold. The headerpressure profile shows the effect of frictional losses over the first1.25″ inches prior to the first gate, with the Reynolds number in the8000 range (turbulent). The static pressures climb from the beginning ofeach gate (lower position value) to the end of the gate, despitefriction losses. There are friction losses in the header between gates.The use of decreasing gates cross-sectional area in the direction offlow in the header to compensate for the changes in the header staticpressure leads to the good distribution from gate to gate. FIG. 491shows the pressure profile from Example 3 in the header (round dots) andin the gates (squares) plotted versus position from the inlet of thechannel.

The gate turning losses are needed to compensate for the pressureprofile created by the changes in flow regime. At the first gate theupstream and downstream Reynolds numbers are 8054 and 5386,respectively, well into turbulent flow regimes. The static pressureincrease for the first gate in that section is dramatic, 1600 Pa, makingup for the friction losses of the channel up to that point. The secondgate has upstream and downstream Reynolds numbers of 5386 and 2699,which start in the turbulent range and drop into the transition range.The pressure gain at the second gate is 400 Pa, a substantial drop fromthe turbulent case. The third gate has upstream and downstream Reynoldsnumbers of 2699 and 0, which implies the flow starts in the transitionflow range and end in laminar range. The pressure gain at the third gateis on the order of 160 Pa, a substantial drop from the second and firstgate's static pressure gains of 400 Pa and 1600 Pa, respectively. Thisexample shows that the effect of momentum compensation on the staticpressure profile, and in turn illustrates the need to use turning lossesto equalize the pressures across the gates. It also illustrates the highflow rates needed to supply millisecond contact time microchannelreactors can lead to very large Reynolds numbers in the M2M manifoldwhen multiple channels must have high overall flow rates that are in thetransition and turbulent ranges. These flow regimes have large headvalues that give rise to substantial momentum compensation and turningloss terms, as this example shows.

EXAMPLE 4 M2M Patent Manifold Performance Comparison

In the following discussion, inventive manifolds are compared withdesigns of the type disclosed by Golbig et al. in WO 03/043730 A1. Themanifold options for a L-manifold with a 72 connecting channel matrixwere evaluated using a manifold design tool. The three options were asfollows: a manifold split into sub-manifolds with gate connectingchannel interfaces, a grate design with one large manifold width andconstant channel opening and channel matrix dimensions, and a gratedesign with one large manifold width and channel widths varying fromchannel to channel (like those discussed in Golbig et al). All thedesigns had the same inlet mass flow rate and target mass flux ratedistribution (akin to contact time). Some results follow:

The sub-manifold design using variable width gates for sub-manifold flowdistribution had the lowest quality index factor (Q₁=6.03%), but had arelatively high manifold pressure drop over inlet head ratio (8.8) dueto the gate M2M turning losses. The pressure drop was estimated at 3.25psid from the macro manifold to the outlet. The final width of themanifold was 3.45″, with 3.15″ actual open space. It is possible tofurther improve this design for lower quality index factors.

The option of a grate design with a single M2M manifold and constantconnecting channel width dimensions had poor quality index factors formost gate widths, obtaining values of Q₁=41.08% to 29.03% for M2M widthsof 2.5 inches to 3.5 inches.

The third option was a grate design with a single M2M manifold with theoption of varying the connecting channel width as that used by Golbig etal. This design was not able to match the low quality index factor ofthe sub-manifold and gate design. It reached a low of Q₂=12.8% with a2.00″ wide manifold, which greatly lowered the manifold pressure drop tohead ratio down to 3.9. Large changes in channel width are needed toobtain reasonable control, i.e. large values of Ra were needed to obtaingood flow distribution.

Common Manifold Features

There are 72 channels, whose total width must add up to 11.52″(=72×0.160″) The walls (i.e ribs) in between the channels make the totalmanifold length add up to 16.800″. The matrix channels are 0.017″ inheight, while the manifold-to-connecting channel opening is 0.023″ tall.In between these two zones there is a short length 0.040″ tall. There isa 1″ long zone upstream of the manifold and all systems have a commonmacro-to-M2M turning loss. All manifold sections have a total height of0.040″ (1.016 mm). The grate systems assume a 0.023″ zone (shim) liesbeneath the 0.040″ tall manifold section, with the grate extendingacross the entire M2M manifold width. A total of 0.00494 kg/second ofair was sent through all three systems at 20° C., with an outletpressure of 101.325 kPa.

Sub-Manifolds with Gate System

The sub-manifold system dimensions, both M2M channel widths and gatewidths, are given in Table 1.

TABLE 1 The sub-manifold and gate design dimensions. M2M Sub- channelmanifold width Width of Gates (inches) number (in) #1 #2 #3 1 0.4000.270 0.250 0.245 2 0.500 0.272 0.255 0.251 3 0.500 0.352 0.330 0.325 40.550 0.390 0.363 0.358 5 0.600 0.368 0.349 0.342 6 0.600 0.580 0.4400.430

The resulting manifold parameters for this case are: The height of theM2M channel (h_(M2M)) is 1.016 mm. The total length of the manifold is16.800″ in total, and each L_(M2M) value is 2.700″ for eachsub-manifold. The ratio of the length of the channels between the end ofthe gate and the 11.5 inch long section to L_(M2M) is 0.23-1.66, basedupon sub-manifold lengths. The sub-manifold Mo values ranged from 0.70to 0.77. The Q₁ values for the connecting channel and sub-manifolds are6.0% and 0.3%, respectively. The Ra value for the system's gates are2.36 and the manifold's pressure drop is 8.83 times its inlet head.

The Grate with Constant Channel Widths

Performance was calculated with all channel widths set to 0.160 inch.The results are shown in Table 2. The table shows improvement in thequality index factor with increasing channel width, but the overall Qfactors are very large. The major driving force for the poordistribution is the turning losses from the M2M manifold to thechannels. These turning loss values are large at the entrance of themanifold due to the large flow rates seen there, adding substantial flowresistance to these channels. This in turn causes flow to skew to thechannels at the end of the manifold.

TABLE 2 Constant channel width results for various manifold widthsManifold Quality index factor Width Q Manifold pressure drop (inches)(%) Over inlet head ratio Mo value 2.50 41.08 5.886 0.141 2.75 37.955.983 0.137 3.00 34.82 6.064 0.134 3.15 33.12 6.102 0.132 3.25 31.856.131 0.131 3.50 29.03 6.191 0.128Grate Design with Channel Widths Varying from Channel to Channel

Channel widths distribution added up to a total width of 11.52 inches oftotal channel width. Basing the channel width on channel number i

$\begin{matrix}{{{Width}\lbrack i\rbrack} = {M + {L\left\lbrack \frac{{i - 36.5}}{36.5 - 1} \right\rbrack}^{B}}} & (1)\end{matrix}$

where M is the median channel width value, L [inches] is the offset fromthe medium width, i is the channel number, and B is the power factor forchanging the channel distribution. L is positive for i<36 and negativefor i>36. This equation (11) allows the distribution to be varied fromlinear to various curves from the median value of 0.160″.

The results are shown in Table 3 for various M2M channel widths. Aninteresting trend appears—as the M2M channel width decreases, bettercontrol of the streams is obtained, up to a minimum value of about2.00″. This is due to the larger connection to manifold cross-sectionalarea ratios (connection openings to manifold) seen at thinner M2Mmanifold widths. As the connection to manifold cross-sectional arearatio increases, the turning losses decrease in pressure drop. Thatcoupled with the relative decrease in connecting channel matrix flowresistance as the channels approach parallel plates for a set channelheight, the net effect is less resistance to flow for the first channelsin the system. FIG. 501 shows the mass flux rate distribution versuschannel position in the manifold for the best case at 2.0″ wide. Forsmaller M2M widths the momentum compensation static pressure increaseseroded the control that the changing width provided.

TABLE 3 Varying channel width results Manifold Ratio of M2M PressureDrop widest to Manifold Quality Index Over thinnest Width M L Factor Q₂Inlet head channels, (inches) (inches) (inches) B (%) Mo ratio Ra 1.750.160 0.100 0.50 16.83 0.156 3.7 4.3 2.00 0.160 0.120 0.50 12.77 0.1503.9 7.0 2.25 0.160 0.120 0.50 14.81 0.145 4.2 7.0 2.50 0.160 0.120 0.7517.35 0.141 4.5 7.0 2.75 0.160 0.120 0.75 18.79 0.137 4.7 7.0 3.00 0.1600.120 0.75 19.15 0.134 4.9 7.0 3.15 0.160 0.120 0.75 18.73 0.132 5.0 7.0

The channel width distribution shown in the Ra ratio was high for all ofthe cases. To get a good distribution with changing channels widths, youwould need a large change in channel width. This may not be feasible forall processing cases or for fabrication of large numbers of thesemanifolds.

In summary, the quality index factors, Ra and Mo ratios for the threecases discussed above are listed in Table 4.

TABLE 4 Summary of case comparison for the 72 channel L-manifoldConnecting channel quality index Ra Mo Case factor (%) ratio ratioSub-manifolds with varying gates Q₁ = 6.0% 2.4 0.74 widths and constantconnecting channel widths Single grate manifold with Q₁ = 29.0% 1.0 0.13constant connecting channel widths Single grate manifold with Q₂ = 12.8%7.0 0.15 varying connecting channel widths

EXAMPLE 5

For a variable width connecting channel M2M manifold, what is therelationship between the connecting channel quality index factor Q₂ andthe Ra and pressure drop ratio? Based on the variable channel widthdesign shown in Golbig, WO 03/043730, Quality index factor wascalculated as a function of the ratio of the area of the largest to thesmallest channel (Ra) and two values of manifold pressure drop ratiodiscussed in the glossary section. While Example 4 was based upon afixed connecting channel length, the results shown below reflectchanging length which in turn changes the connecting channel backpressure. The results show the effect of channel width change upon flowdistribution as a function of channel back pressure.

FIG. 511 shows the minimum quality index factors, based upon thedimensions discussed in Example 4, plotted versus connecting channelpressure drop over manifold pressure drop.

The Ra=1 curve shows constant channel width Q2 values, and predictablyyou can achieve small Q₂ factors for this system as the pressure drop inthe channel increases. If the connecting channel pressure drop is largeenough, special manifold designs may not be necessary.

As the Ra value increases from unity the Q factors for the pressure dropratio increasing from zero fall to a minimum below the Ra=1 value. Thus,for a given back pressure, there may be a non unity Ra value that givesa better Q factor than the Ra=1 value

However, as values of the pressure drop ratio increase, the Q₂ curves ofconstant Ra cross over the Ra=1 curve and to asymptote to values higherthan the Ra=1 values. However, if the lengths of the channels of varyingwidth get long enough, a maldistribution will occur due to differingresistance in the channel flow resistance.

FIG. 521 shows the same quality index factor data plotted versus theratio of connecting channel pressure drop over the manifold inlet head,and while the curves change slightly, the general trends stay the same.The Q₂ surface in FIGS. 2A1-2D1 based upon Ra and DPR₁ is made by theconstant Ra values correlations based on the curves in FIG. 521 andLagrangian interpolation between these values to get a representativecurve of best cases Q_(c):

Q _(c)(Ra,DPR ₁)=E1+E2+E4+E6+E8+E10+E12,

where

${E\; 1} = {\frac{112.9 + {1.261{DPR}_{1}}}{1 + {0.3078\; {DPR}_{1}} + {0.003535\; {DPR}_{1}^{2}}}\left\lbrack \frac{\begin{matrix}{\left( {{Ra} - 2} \right)\left( {{Ra} - 4} \right)\left( {{Ra} - 6} \right)} \\{\left( {{Ra} - 8} \right)\left( {{Ra} - 10} \right)\left( {{Ra} - 12} \right)}\end{matrix}}{\begin{matrix}{\left( {1 - 2} \right)\left( {1 - 4} \right)\left( {1 - 6} \right)} \\{\left( {1 - 8} \right)\left( {1 - 10} \right)\left( {1 - 12} \right)}\end{matrix}} \right\rbrack}$${E\; 2} = {\frac{91.73 - {1.571{DPR}_{1}} + {0.01701{DPR}_{1}^{2}}}{1 + {0.2038{DPR}_{1}} + {0.00193{DPR}_{1}^{2}}}\left\lbrack \frac{\begin{matrix}{\left( {{Ra} - 1} \right)\left( {{Ra} - 4} \right)\left( {{Ra} - 6} \right)} \\{\left( {{Ra} - 8} \right)\left( {{Ra} - 10} \right)\left( {{Ra} - 12} \right)}\end{matrix}}{\begin{matrix}{\left( {2 - 1} \right)\left( {2 - 4} \right)\left( {2 - 6} \right)} \\{\left( {2 - 8} \right)\left( {2 - 10} \right)\left( {2 - 12} \right)}\end{matrix}} \right\rbrack}$${E\; 4} = {\frac{24.27 - {4.943{DPR}_{1}} + {0.3982{DPR}_{1}^{2}}}{\begin{matrix}{1 - {0.2395{DPR}_{1}} + {0.03442{DPR}_{1}^{2}} -} \\{0.000006657{DPR}_{1}^{3}}\end{matrix}}\left\lbrack \frac{\begin{matrix}{\left( {{Ra} - 1} \right)\left( {{Ra} - 2} \right)\left( {{Ra} - 6} \right)} \\{\left( {{Ra} - 8} \right)\left( {{Ra} - 10} \right)\left( {{Ra} - 12} \right)}\end{matrix}}{\begin{matrix}{\left( {4 - 1} \right)\left( {4 - 2} \right)\left( {4 - 6} \right)} \\{\left( {4 - 8} \right)\left( {4 - 10} \right)\left( {4 - 12} \right)}\end{matrix}} \right\rbrack}$${E\; 6} = {\frac{29.23 - {2.731{DPR}_{1}} + {0.09734{DPR}_{1}^{2}}}{1 - {0.1124{DPR}_{1}} + {0.005045{DPR}_{1}^{2}}}\left\lbrack \frac{\begin{matrix}{\left( {{Ra} - 1} \right)\left( {{Ra} - 2} \right)\left( {{Ra} - 4} \right)} \\{\left( {{Ra} - 8} \right)\left( {{Ra} - 10} \right)\left( {{Ra} - 12} \right)}\end{matrix}}{\begin{matrix}{\left( {6 - 1} \right)\left( {6 - 2} \right)\left( {6 - 4} \right)} \\{\left( {6 - 8} \right)\left( {6 - 10} \right)\left( {6 - 12} \right)}\end{matrix}} \right\rbrack}$

${E\; 8} = {\frac{\begin{matrix}{25.98 + {11.26{DPR}_{1}^{2}} +} \\{{0.02201{DRP}_{1}^{2}} + {0.5231{DPR}_{1}^{3}}}\end{matrix}}{\begin{matrix}{1 - {0.8557{DPR}_{1}} + {0.00887{DPR}_{1}^{2}} +} \\{{0.02049{DPR}_{1}^{3}} - {0.000002866{DPR}_{1}^{4}}}\end{matrix}} \times \left\lbrack \frac{\begin{matrix}{\left( {{Ra} - 1} \right)\left( {{Ra} - 2} \right)\left( {{Ra} - 4} \right)} \\{\left( {{Ra} - 6} \right)\left( {{Ra} - 10} \right)\left( {{Ra} - 12} \right)}\end{matrix}}{\begin{matrix}{\left( {8 - 1} \right)\left( {8 - 2} \right)\left( {8 - 4} \right)} \\{\left( {8 - 6} \right)\left( {8 - 10} \right)\left( {8 - 12} \right)}\end{matrix}} \right\rbrack}$ ${E\; 10} = {\frac{\begin{matrix}{20.75 - {3.371{DPR}_{1}} +} \\{{0.9026{DPR}_{1}^{2}} + {0.01277{DPR}_{1}^{3}}}\end{matrix}}{\begin{matrix}{1 - {0.1514{DPR}_{1}} + {0.03173{DPR}_{1}^{2}} +} \\{0.0003673{DPR}_{1}^{3}}\end{matrix}}\left\lbrack \frac{\begin{matrix}{\left( {{Ra} - 1} \right)\left( {{Ra} - 2} \right)\left( {{Ra} - 4} \right)} \\{\left( {{Ra} - 6} \right)\left( {{Ra} - 8} \right)\left( {{Ra} - 12} \right)}\end{matrix}}{\begin{matrix}{\left( {10 - 1} \right)\left( {10 - 2} \right)\left( {10 - 4} \right)} \\{\left( {10 - 6} \right)\left( {10 - 8} \right)\left( {10 - 12} \right)}\end{matrix}} \right\rbrack}$ ${E\; 12} = {\frac{\begin{matrix}{51.67 + {18.94{DPR}_{1}} +} \\{{21.57{DPR}_{1}^{2}} + {21.57{DPR}_{1}^{3}}}\end{matrix}}{\begin{matrix}{1 + {1.183{DPR}_{1}} + {0.5513{DPR}_{1}^{2}} -} \\{0.0000459{DPR}_{1}^{3}}\end{matrix}}\left\lbrack \frac{\begin{matrix}{\left( {{Ra} - 1} \right)\left( {{Ra} - 2} \right)\left( {{Ra} - 4} \right)} \\{\left( {{Ra} - 6} \right)\left( {{Ra} - 8} \right)\left( {{Ra} - 10} \right)}\end{matrix}}{\begin{matrix}{\left( {12 - 1} \right)\left( {12 - 2} \right)\left( {12 - 4} \right)} \\{\left( {12 - 6} \right)\left( {12 - 8} \right)\left( {12 - 10} \right)}\end{matrix}} \right\rbrack}$

Following from the above description and invention summaries, it shouldbe apparent to those of ordinary skill in the art that, while themethods and apparatuses herein described constitute exemplaryembodiments of the present invention, the invention contained herein isnot limited to this precise embodiment and that changes may be made tosuch embodiments without departing from the scope of the invention asdefined by the claims. Additionally, it is to be understood that theinvention is defined by the claims and it is not intended that anylimitations or elements describing the exemplary embodiments set forthherein are to be incorporated into the interpretation of any claimelement unless such limitation or element is explicitly stated.Likewise, it is to be understood that it is not necessary to meet any orall of the identified advantages or objects of the invention disclosedherein in order to fall within the scope of any claims, since theinvention is defined by the claims and since inherent and/or unforeseenadvantages of the present invention may exist even though they may nothave been explicitly discussed herein.

1. An apparatus for carrying out a reaction for the formation ofhydrogen peroxide comprising: a first channel adapted to carry anoxidant stream comprising an oxidant; a second channel adapted to carrya hydrogen source stream comprising a hydrogen source; and a firstmicrochannel downstream from and in fluid communication with the firstchannel and the second channel, the first microchannel at leastpartially containing a catalyst adapted to facilitate a reaction betweenthe hydrogen source and the oxidant to generate hydrogen peroxide. 2.The apparatus of claim 1, wherein the first channel is a microchannelmanifold operative to direct the oxidant stream into the firstmicrochannel.
 3. The apparatus of claim 2, wherein the microchannelmanifold is operative to direct the oxidant stream into the firstmicrochannel at multiple points along the length of the firstmicrochannel.
 4. The apparatus of claim 1, further comprising a mixingconduit in fluid communication with the first microchannel, the firstchannel, and the second channel, the mixing conduit operative to allowthe oxidant stream to mix with the hydrogen source stream.
 5. Theapparatus of claim 1, further comprising: a third channel adapted tocarry an oxidant stream comprising an oxidant; a fourth channel adaptedto carry a hydrogen source stream comprising a hydrogen source; and asecond microchannel downstream from and in fluid communication with thethird channel and the fourth channel, the second microchannel at leastpartially containing a catalyst adapted to facilitate a reaction betweenthe hydrogen source and the oxidant to generate hydrogen peroxide. 6.The apparatus of claim 5, wherein: an output stream of the firstmicrochannel flows into an output stream of the second microchannelcarrying hydrogen peroxide produced in the first and secondmicrochannels; and the first channel, the second channel, the thirdchannel, the fourth channel, the first microchannel, and the secondmicrochannel comprising a reactor repeating unit.
 7. The apparatus ofclaim 6, further comprising a heat transfer conduit in thermalcommunication with the reactor repeating unit, the heat transfer conduitadapted to have a heat transfer fluid flowing therethrough.
 8. Theapparatus of claim 6, wherein the output stream includes a microchanneloutput stream.
 9. The apparatus of claim 1, wherein the firstmicrochannel is a continuation of the first channel.
 10. The apparatusof claim 1, wherein: the first microchannel includes an input sectionwhere the oxidant stream and the hydrogen source stream are introducedprior to reacting in the presence of the catalyst; the firstmicrochannel is in thermal communication with a heat transfer conduitadapted to have a heat transfer fluid flowing therethrough.
 11. Theapparatus of claim 10, wherein: the oxidant stream enters the inputsection from a first side; the hydrogen source stream enters the inputsection from a second side; and the first side is generally opposite thesecond side.
 12. The apparatus of claim 10, wherein: the oxidant streamand hydrogen source stream enter the input section on a same side; andthe oxidant stream enters the input section downstream from where thehydrogen source enters the input section.
 13. The apparatus of claim 1,wherein the second channel is a microchannel manifold operative todirect the hydrogen source stream into the second microchannel.
 14. Theapparatus of claim 13, wherein the microchannel manifold is operative todirect the hydrogen source stream into the second microchannel atmultiple points along the length of the second microchannel.
 15. Theapparatus of claim 1, further comprising: a heat transfer conduit inthermal communication with the first microchannel, the heat transferconduit adapted to have a heat transfer fluid flowing therethrough; apressurized vessel at least partially containing the first microchanneland at least partially containing the heat transfer conduit therein, thepressurized vessel adapted to house a pressurized fluid exerting apositive pressure upon the first microchannel.
 16. The apparatus ofclaim 1, wherein the first microchannel includes a fluid flow obstaclein series therewith to suppress turbulence.
 17. An apparatus forcarrying out a reaction for the formation of hydrogen peroxidecomprising: a first channel adapted to carry an oxidant streamcomprising an oxidant; a second channel adapted to carry a hydrogensource stream comprising a hydrogen source; a first microchanneldownstream from and in fluid communication with the first channel andthe second channel, the first microchannel at least partially containinga catalyst adapted to facilitate a reaction between the hydrogen sourceand the oxidant to generate hydrogen peroxide; a microchannel outputconduit downstream from, and in fluid communication with, the firstmicrochannel for carrying an output fluid including the generatedhydrogen peroxide; a semipermeable structure in concurrent communicationwith the microchannel output conduit and a microchannel adsorbantconduit, wherein the semipermeable structure is operative to separateliquid from gas within the output fluid so that the hydrogen peroxideand liquid from the output fluid flow into the microchannel adsorbantconduit.
 18. The apparatus of claim 17, wherein the semipermeablemembrane includes a wetted wick.
 19. The apparatus of claim 17, furthercomprising a gas outlet conduit in communication with the microchanneloutput conduit to carry away the gases of the output fluid not passingthrough the semipermeable membrane.
 20. The apparatus of claim 17,wherein: a fraction of the gases from the output fluid are dissolved inthe liquid of the output fluid; and the fraction of the gases from theoutput fluid that are dissolved in the liquid of the output fluid passthrough the semipermeable membrane.